KP Technology's Publication Database

Timestamp System Used Title Of Paper Authors Journal Title Date Abstract URL Keywords
Timestamp System Used Title Of Paper Authors Journal Title Date Abstract URL Keywords
02/06/14 17:05 RHC020 Effect of annealing temperature on surface morphology and work function of ZnO nanorod arrays Hainan Wua, Mingshan Xuea, Corresponding author contact information, E-mail the corresponding author, Junfei Oua, b, Fajun Wanga, Wen Lia, Journal of All oys and Compounds 2013 A simple and effective method of fabricating nanomaterials and the understanding of their electronic structures are significant for designing novel nanodevices. In this study, ZnO nanorod arrays on ITO substrate were synthesized by electrochemical deposition, and the effect of annealing temperature on surface morphology and especially work function was investigated using various techniques. The results indicated that the formation of hexagonal ZnO nanorod arrays with (0 0 0 1) orientation was strongly associated with the annealing temperature. The work function of well-aligned ZnO nanorod arrays is 4.84 eV, which shows an obvious dependence on the arrangement of ZnO nanorod arrays. These changes in work function of ZnO nanorod arrays (e.g., used as the photoanode of dye-sensitized solar cells) are important to understand the electron transport of related nanodevices. http://www.sciencedirect.com/science/article/pii/S0925838813005148 ZnO; Nanorod arrays; Work function; Annealing temperature
11/05/14 11:15 KP020 Annealing Effect of ZnO on the Performance of Inverted Organic Photovoltaic Devices Wenjing Qin, Guojing Ding, Xinrui Xu, Liying Yang and Shougen Yin Journal of Materials Science and Technology (30:2), 2014, pp.197-202 Feb-14 ZnO nanoparticles films were prepared via sol‰ÛÒgel process and incorporated into inverted organic photovoltaic devices with a structure of ITO/ZnO/P3HT:PCBM/MoO3/Ag, in which ZnO film served as an electron selective layer. The effects of annealing temperature of ZnO film on the device performance were investigated. When the annealing temperature was 300 å¡C, a well-arranged ZnO thin film was obtained, and the optimized device had doubled short circuit current density (JSC) and seven-fold higher power conversion efficiency (PCE) compared to the devices without ZnO film. This improvement could be attributed to the enlarged interfacial area of ZnO/active layer and better energy band matching which causes an efficient electron extraction and a decreased interface energy barrier. At particularly high annealing temperature, dramatically increased sheet resistance of indium tin oxide (ITO) was found to cause PCE deterioration. Our finding indicates that it is highly important to investigate both morphology and electrical effects for understanding and optimizing organic photovoltaic (OPV) performance. http://www.sciencedirect.com/science/article/pii/S1005030213001795 ZnO; Inverted organic photovoltaic; Annealing effect
1/13/2014 15:02:13 SKP 5050 Growth and gas sensing characteristics of p- and n-type ZnO nanostructures N.S. Ramgir, M. Ghosh, P. Veerender, N. Datta, M. Kaur, D.K. Aswal, S.K. Gupta Sensors and Actuators B: Chemical, Volume 156, Issue 2, August 2011, Pages 875‰ÛÒ880 2011 ZnO nanoparticles (NPs) of 5‰ÛÒ15 nm size and nanowires (NWs) of 50‰ÛÒ100 nm dia., exhibiting p and n-type characteristics, respectively, have been synthesized using simple chemical process. ZnO NW-films exhibited good sensitivity and selectivity towards H2S in ppm range with fast response and recovery times. Interestingly, ZnO NP-films showed p-type conductivity that has been obtained for the first time without intentional doping while NW-films showed n-type conduction as has also been reported in various earlier studies. The p- and n-type conductivities in NP- and NW-films have been confirmed using hot probe and Kelvin probe measurements. The n-type behavior of NW-films is attributed to oxygen vacancies, whereas the p-type nature of NP-films is attributed to the zinc vacancy, surface acceptor levels created by the adsorbed oxygen and/or the unintentional carbon doping in ZnO. http://www.sciencedirect.com/science/article/pii/S0925400511001808 ZnO, nanoparticles, nanowires, gas sensor, H2S, p-type semiconductor
1/13/2014 14:17:32 SKP 5050 Room temperature H2S sensor based on Au modified ZnO nanowires Niranjan S. R amgir, Preetam K. Sharma, N. Datta, M. Kaur, A.K. Debnath, D.K. Aswal, S.K. Gupta Sensors and Actuators B 186 (2013) 718‰ÛÒ 726 2013 A room temperature H2S sensor based on pure and Au modified ZnO nanowires has been demonstrated. Modification of ZnO nanowires with Au resulted in a remarkable 16-fold increase in the sensor response over pure ZnO NWs toward 5 ppm H2S at room temperature. A sensing mechanism based on the formation of nano-Schottky type barrier junction at the interface between Au and ZnO has been proposed. The enhanced response is attributed to the alteration of barrier properties by the adsorption or desorption of adsorbed species and/or H2S gas molecules. Observance of higher resistivity and a higher work function (0.2 eV) for Au modified samples further corroborates the finding. Low temperature resistivity measurements indicate that the charge transport is governed by the thermal conduction and the nearest neighbor hopping mechanism. http://www.sciencedirect.com/science/article/pii/S092540051300751X ZnO nanowires, Schottky type barrier junction, H2S, sensors, work function
11/04/14 21:03 SKP5050 Surface photovoltage analysis of ZnO nanorods/p-Si heterostructure Dawei Kang, Jiming Bian, Yongchang Sang, Aimin Liu, Jingchang Sun, Jun Xuan Materials Science in Semiconductor Processing (16:2), 2013, pp. 520-524 Apr-13 In this work, n-type ZnO nanorods (NRs) were fabricated on a p-type Si substrate to form a ZnO NRs/Si structure using a low-temperature wet chemical bath deposition method. Kelvin-probe-based surface photovoltage (KP-based SPV) technology was used to study the behavior of surface photogenerated charges for the as-grown heterostructure. In general, the KP-based SPV response range of the ZnO NRs/Si structure was significantly expanded compared with the bare Si substrate, due to the incorporation of ZnO NRs. Moreover, the SPV response amplitude for ZnO NRs/Si structure also depended on the length and diameter of the NRs, and the corresponding mechanism was elucidated in terms of O2 adsorption. The photovoltaic application of the ZnO NRs/Si based structure would benefit significantly from these achievements. http://www.sciencedirect.com/science/article/pii/S1369800112002612 ZnO nanorod; Si; Surface photovoltage; Kelvin probe
1/13/2014 14:50:16 KP 020 Surface studies of crystalline and amorphous Zn‰ÛÒIn‰ÛÒSn‰ÛÒO transparent conducting oxides Diana E. Prof fit, Steven P. Harvey, Andreas Klein, Robert Schafranek, Jonathan D. Emery, D. Bruce Buchholz, Robert P.H. Chang, Michael J. Bedzyk, Thomas O. Mason Thin Solid Films 520 (2012) 5633‰ÛÒ5639 2012 X-ray and ultraviolet photoelectron spectroscopy (UPS) studies were made of in situ RF magnetron-sputtered crystalline (c) and amorphous (a) Zn‰ÛÒIn‰ÛÒSn‰ÛÒO (ZITO) thin films, ex situ pulsed laser deposited c- and a-ZITO thin films, and bulk ZITO ceramics. Cosubstitution of Zn and Sn for In results in an increase of the In core level binding energy at a given Fermi level compared to that measured in undoped and Sn-doped In2O3 (ITO). In plots of work function vs. Fermi level, in situ c-ZITO and a-ZITO films have low ionization potentials (7.0‰ÛÒ7.7 eV) that are similar to undoped In2O3. In contrast, dry-air-annealed in situ films, ex situ films, and bulk ceramics have higher ionization potentials (7.7‰ÛÒ8.1 eV) that are more similar to ITO and match well with previous work on air-exposed surfaces. Kelvin Probe measurements were made of select a-ZITO films exposed to air and ultraviolet/ozone-treated so as to measure work functions under conditions commonly employed for device fabrication. Results (4.8‰ÛÒ5.3 eV) were in good agreement with the UPS work functions of oxygen-exposed materials and with literature values. Lastly, a parallelogram plot of work function vs. Fermi level shows that a wider range of work functions is achievable in ZITO materials as compared to other transparent conducting oxides (Sb-doped SnO2, Al-doped ZnO, Sn-doped In2O3), making ZITO more versatile for applications. http://www.sciencedirect.com/science/article/pii/S0040609012005366 ZITO, thin films, work function, Fermi level
3/31/2015 9: 09:10 SKP5050 Relationship between Dissolved Oxygen and Corrosion Characterization of X80 Steel in Acidic Soil Simulated Solution Shuaixing W ang, Daoxin Liu, Nan Du, Qing Zhao, Shuyun Liu and Jinhua Xiao International Journal of Electrochemical Science (10), 2015, pp.4393 - 4404 2015 The relationship between dissolved oxygen (DO) and corrosion behavior of X80 steel in acidic soil simulated solution was studied by potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning Kelvin probe technique (SKP) and XRD. Results showed that the presence of DO accelerated the cathodic process of corrosion for X80 steel in the acidic soil simulated solution. With the decrease of DO, 1/Rct and icorr decreased gradually, the corrosion rate of X80 steel reduced. The corrosion of X80 steel was controlled by the ionization reaction when the content of DO in solution was bigger than 1.90 ppm. However, the diffusion of oxygen dominated the corrosion process of X80 steel in simulated solution with 0.85 ppm DO, as demonstrated by the presence of cathodic limiting diffusive current and Warburg impedance. Besides, DO could affect the formation and composition of the corrosion product formed on X80 steel. In O2-saturated solution, a homogeneous and compact corrosion product layer, ë³-FeOOH and Fe3O4, formed on the surface of X80 steel. But the phase composition of corrosion product was ë³-FeOOH, Fe2O3 and a few FeCO3 when DO in solution was 0.85 ppm. http://electrochemsci.org/papers/vol10/100504393.pdf X80 steel; acidic soil; Corrosion; Dissolved oxygen; Electrochemical impedance spectroscopy (EIS); Scanning Kelvin probe (SKP)
02/06/14 17:07 RHC020 Understanding of the correlation between work function and surface morphology of metals and alloys Mingshan Xu eCorresponding author contact information, E-mail the corresponding author, Wenfeng Wang, Fajun Wang, Junfei Ou, Changquan Li, Wen Li Journal of All oys and Compounds Volume 577, 15 November 2013, Pages 1‰ÛÒ5 2013 The relationships between material behaviors and its structures are extremely complicated, and the understanding of these relationships is of much significance for revealing the physical, chemical and mechanical properties of various materials. In this study, the change of the work function (WF) of metals and alloys as a function of surface roughness was investigated by scanning Kelvin probe, with the aim of understanding the inherent correlation between the WF and surface morphology using a simple and intuitive way. It was demonstrated that at the rough surface of Cu and Ag, the sharp micro/nanostructures induced a lower WF, just as the lightning rod effect providing a direct and fast path for electron transport. While for Al and Mg alloys, the rough surface resulted in an increase of the WF owing to the effect of surface oxide layers, just as the anti-lightning rod effect providing a protected layer to confine the electron transport. http://www.sciencedirect.com/science/article/pii/S0925838813010256 Work function; Surface morphology; Lightning rod effect
02/06/14 17:02 RHC020 Characterization of interfacial strength of dissimilar metallic joints using a scanning Kelvin probe Mingshan Xu e, Juan Xie, Wen Li,‰àÔ Junfei Ou, Fajun Wang and Zhenchen Zhong Scripta Materialia 66 (2012) 265‰ÛÒ268 2011 Mingshan Xu e, Juan Xie, Wen Li,‰àÔ Junfei Ou, Fajun Wang and Zhenchen Zhong http://www.sciencedirect.com/science/article/pii/S1359646211006890 Work function; Interfacial tensile strength; Kelvin probe; Dissimilar joints
02/06/14 17:09 RHC020 Self-assembly growth and electron work function of copper phthalocyanine films on indium tin oxide glass Mingshan Xu ea, b, Corresponding author contact information, E-mail the corresponding author, Zhonghao Jiangb, Corresponding author contact information, E-mail the corresponding author, Wen Lia, b, Guangli Bib, Junfei Oua, Fajun Wanga, Changquan Lia Applied Surface Science Volume 258, Issue 8, 1 February 2012, Pages 3373‰ÛÒ3377 2012 Organic semi conductor materials are becoming a promising subject of not only scientific interest but also potential applications in the field of new energy resources. In this study, the copper phthalocyanine (CuPc) films as an excellent organic semiconductor were self-assembly grown on indium tin oxide glass by electrodeposition, the structural and electronic properties were investigated using various techniques. The results demonstrated that ordered ë±-form crystalline CuPc films were obtained. The decrease of electron work function of CuPc films with the increase of film thickness was found, which was obviously dependent on the surface morphology. The understanding of these behaviors of CuPc films will be significant for designing related photoelectric devices. http://www.sciencedirect.com/science/article/pii/S0169433211017314 Work function; Electronic structures; Copper phthalocyanine
10/02/14 15:51 SKP5050 Work function changes of plasma treated indium tin oxide Kongduo He, Xilu Yang, Hang Yan, Zhonghang Wu, Zebin Li, Shaofeng Zhong, Qiongrong Ou, Rongqing Liang Organic Electronics May-14 The work function (WF) changes of indium tin oxide (ITO) treated by O2 or Cl2 plasma were invested. The WF firstly decreases in an exponential way for 2‰ÛÒ6 h and subsequently in a linear way for days in air after plasma treatment. X-ray photoelectron spectroscopy (XPS) shows the dipole layer formed by O‰ÛÒIn and O‰ÛÒO bonds in the ITO surface treated by O2 plasma increases the WF. Exposed in vacuum, the O‰ÛÒO bonds tend to break and the reactive O species reduce in the oxidized ITO surface, accounting for the exponential decrease of WF. The environment preserving the chlorinated or oxidized ITO is important to slow down the decrease of WF. The mechanism for WF changes of plasma treated ITO is significant to investigate the properties of organic optoelectronic devices. http://dx.doi.org/10.1016/j.orgel.2014.05.008 Work Function, Plasma, Indium tin oxide, Exponential decrease, Linear decrease, First order reaction
12/16/2014 9:41:57 KP020 Optical Parameters and Work Function of Zn-In-Sn-O Films Seunghun Lee, Hyomin Park, Young Do Kim, Sung Ju Tark, Yoonmook Kang, Won Mok Kim, Hae-Seok Lee and Donghwan Kim Current Applied Physics, 2014 Dec-14 The work function behavior of Zn-In-Sn-O (ZITO) films with various Zn and Sn contents were studied. The work function increased with addition of Zn content. With further increase of Zn contents, the work function gradually decreased. The work function behavior can be investigated by (1) Fermi level position relative the carrier concentration, (2) ionization potential by the surface dipole change. The Fermi level position related the carrier concentration was calculated by Drude parameters, and ionization potential measured by UPS. As results, we confirmed that the work function of ZITO may be linked to changes in ionization potential, not carrier concentration. http://www.sciencedirect.com/science/article/pii/S1567173914003940 work function, ITO, Zn-In-Sn-O, sputter, heterojunction solar cell
12/16/2014 14:48:54 KP020 Optical Parameters and Work Function of Zn-In-Sn-O Films Seunghun Lee, Hyomin Park, Young Do Kim, Sung Ju Tark, Yoonmook Kang, Won Mok Kim, Hae-Seok Lee and Donghwan Kim Current Applied Physics Dec-14 The work function behavior of Zn-In-Sn-O (ZITO) films with various Zn and Sn contents were studied. The work function increased with addition of Zn content. With further increase of Zn contents, the work function gradually decreased. The work function behavior can be investigated by (1) Fermi level position relative the carrier concentration, (2) ionization potential by the surface dipole change. The Fermi level position related the carrier concentration was calculated by Drude parameters, and ionization potential measured by UPS. As results, we confirmed that the work function of ZITO may be linked to changes in ionization potential, not carrier concentration. http://www.sciencedirect.com/science/article/pii/S1567173914003940 work function, ITO, Zn-In-Sn-O, sputter, heterojunction solar cell
1/13/2014 14:52:28 SKP + RHC Work Function Analysis of Gas Sensitive WO3 Layers with Pt Doping G. Halek, I.D. Baikie, H. Teterycz, P. Halek, P. Suchorska, K. WiÝniewski IMCS 2012 ‰ ÛÒ The 14th International Meeting on Chemical Sensors 2012 In this paper platinum (Pt) doped tungsten trioxide (WO3) layers have been investigated. The structures were prepared in the standard thick film technology. A scanning electron microscope (SEM) was used for the microstructure analysis of the gas sensitive layers. The work function was examined by using a scanning Kelvin probe (SKP). The Kelvin probe is a non-contact and non-destructive method to provide work function measurements and surface analysis. This tool is very sensitive to any surface potential changes of the investigated material. The measurements preformed by using the SKP shows that the screen printed WO3layers were very homogenous and no significant defects are present. The Pt dopants added to the gas sensitive layer created small clusters on the surface of the WO3 grains. The presence of those additives changes the potential barrier between the metal oxide crystals and caused a decrease of the sensing layer conductance at low dopants concentration, until the exceed of the percolation threshold. Moreover, due to the introduction of additives a change in the activation energy was observed which has influence on the sensor parameters and resulted in increase of the sensitivity to isopropyl alcohol. http://www.sciencedirect.com/science/article/pii/S0925400512013718 work function, activation energy change, tungsten trioxide, Pt doping, gas sensors
1/13/2014 14:18:13 SKP 5050 Selective H2S sensing characteristics of CuO modified WO3 thin films Niranjan S. R amgir, C.P. Goyal, P.K. Sharma, U.K. Goutam, S. Bhattacharya, N. Datta, M. Kaur, A.K. Debnath, D.K. Aswal, S.K. Gupta Sensors and Actuators B 188 (2013) 525‰ÛÒ 532 2013 An H2S sensor based on randomly distributed nano p‰ÛÒn junction between CuO and WO3 has been demonstrated. Modification with CuO resulted in enhanced response kinetics towards H2S with high selectivity. CuO modified WO3 thin films corresponding to 2.25 at% of Cu exhibited a sensor response of 534 in comparison to that of pure WO3 thin films that exhibited a sensor response of 21 towards 10 ppm of H2S at an operating temperature of 300 å¡C. This enhanced response kinetics has been attributed to the formation of random nano p‰ÛÒn junctions distributed over the surface of the sensor film and the unique interaction of CuO with H2S. At elevated temperature exposure to H2S resulted in the conversion of CuO to CuS, which being metallic in nature causes a drastic change in the resistance of the sensor films. Formation of nano p‰ÛÒn junctions is supported by the increase in the sensor resistance upon CuO modification and is further corroborated by the work function studies. http://www.sciencedirect.com/science/article/pii/S0925400513008496 WO3, CuO, nano p‰ÛÒn junction, gas sensing, H2S
11/04/14 21:13 SKP5050 High Fill Fact or Polymer Solar Cells Incorporating a Low Temperature Solution Processed WO3 Hole Extraction Layer Tobias Stubh an, Ning Li, Norman A. Luechinger, Samuel C. Halim, Gebhard J. Matt and Christoph J. Brabec Advanced Energy Materials (2:12), 2012, pp. 1433-1438. Dec-12 We demonstrate solution-processed tungsten trioxide (WO3) incorporated as hole extraction layer (HEL) in polymer solar cells (PSCs) with active layers comprising either poly(3-hexylthiophene) (P3HT) or poly[(4,4'-bis(2-ethylhexyl)dithieno[3,2-b:2‰Û²,3‰Û²-d]silole)-2,6-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadiazole)-5,50-diyl] (Si-PCPDTBT) mixed with a fullerene derivative. The WO3 layers are deposited from an alcohol-based, surfactant-free nanoparticle solution. A short, low-temperature (80 å¡C) annealing is sufficient to result in fully functional films without the need for an oxygen-plasma treatment. This allows the application of the WO3 buffer layer in normal as well as inverted architecture solar cells. Normal architecture devices based on WO3 HELs show comparable performance to the PEDOT:PSS reference devices with slightly better fill factors and open circuit voltages. Very high shunt resistances (over 1 Më© cm2) and excellent diode rectification underline the charge selectivity of the solution-processed WO3 layers. http://onlinelibrary.wiley.com/doi/10.1002/aenm.201200330/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false WO3 nanoparticles;WO3 nanoparticle dispersion;anode buffer layer;PEDOT:PSS replacement;organic electronics;photovoltaic devices
11/05/14 11:43 KP020 Preparation of vanadium diselenide thin films and their application in CdTe solar cells Jingjing Gao, Xia Di, Wei Li, Lianghuan Feng, Jingquan Zhang, Lili Wu, Bing Li, Wenwu Wang, Guanggen Zeng and Jiayi Yang Thin Solid Films (550), 2014, pp. 638-642. Jan-14 Vanadium di selenide thin films were prepared by electron beam evaporation. The properties of vanadium diselenide thin films were investigated using X-ray diffraction, scanning electron microscope, transmission spectra, electrical and Hall measurements. To further investigate the application of vanadium diselenide thin films, device performance in CdTe solar cells with a vanadium diselenide layer was also studied. The results indicate that vanadium diselenide thin films had a stable hexagonal structure after annealing. The thin films were p-type semiconductor materials with the high work function and high carrier concentration. Vanadium diselenide thin films could form a good ohmic contact to CdTe solar cells. Thus, cell performance was greatly improved when introduced a vanadium diselenide buffer layer. http://www.sciencedirect.com/science/article/pii/S0040609013016337 Vanadium diselenide; Thin films; Back contact; Cadmium telluride; Solar cells; Electron beam evaporation
11/05/14 09:44 SKP5050 Up-conversion semiconducting MoO3:Yb/Er nanocomposites as buffer layer in organic solar cells Hai-Qiao Wa ng, Tobias Stubhan, Andres Osvet, Ivan Litzov, Christoph J. Brabec Solar Energy Materials and Solar Cells (105), 2012, pp.196-201 Oct-12 The spectral sensitivity of organic solar cells can be sensitized in the near-IR and IR by incorporating Yb/Er-doped MoO3 up-conversion nanocomposites. Poly-3-hexyl thiophene (P3HT) and [6,6] phenyl C61 butyric acid methyl ester (PC61BM) were chosen for the active layer. Yb/Er-doped MoO3 nanoparticles with dual functionality were solution processed as charge selective interface layer. On the one hand, the electrical functionality of MoO3 as hole extraction layer is demonstrated. On the other hand, up-conversion emission from Yb3+ sensitized Er3+ dopants in the MoO3 nanoparticles is observed. Since the photocurrent generated from up-conversion with 975 nm excitation was found to be in competition with photocurrent contributions from a charge transfer complex absorbing also in the near IR, up-conversion from a Yb/Er doped MoO3 layer within an organic solar cell is proven spectroscopically and demonstrated by analyzing the photocurrent response of the Yb/Er doped cell and the undoped cell to the excitation intensity. The concept to integrate up-conversion functionality into metal oxide (MOx) based charge extraction layer suggests a promising and practical pathway for improving the near IR and IR sensitivity of thin film solar cells. http://www.sciencedirect.com/science/article/pii/S0927024812002838 Up-conversion semiconducting MoO3; Solution-processable; Interface layer; Organic solar cell
11/04/14 15:12 SKP5050 A study on photo-generated charges property in highly ordered TiO2 nanotube arrays Yu Zhang, De jun Wang, Shan Pang, Yanhong Lin, Tengfei Jiang and Tengfeng Xie Applied Surface Science (256:23), 2010, pp 7217-7221. Sep-10 In this study TiO2 nanotube arrays were fabricated by potentiostatic anodization of titanium sheet. The X-ray diffraction (XRD) pattern and field emission scanning electron microscopy (FE-SEM) image indicated the TiO2 nanotube arrays were of pure anatase form and highly ordered. The properties of the photo-generated charges in the nanotube arrays were investigated by transient photovoltage (TPV) technique and surface photovoltage (SPV) technique based on lock-in amplifier with dc bias, in comparison with the commercial powder derived film. The separation processes of the photo-induced charges in the system of TiO2 nanotubes on Ti have been demonstrated to be correlated with the incident light intensity, surface trapping states, and the interfacial electric field between Ti and TiO2. The results also show that the highly ordered nanotube film could generate much stronger SPV responses under external electric field than the commercial powder derived film. http://www.sciencedirect.com/science/article/pii/S0169433210007348 Titania nanotube array, photo-generated charge, surface photovoltage
02/06/14 17:22 SKP5050 with SPV Visible light photoelectrocatalysis with salicylic acid-modified TiO2 nanotube array electrode for p-nitrophenol degradation Xin Wang, H uimin ZhaoCorresponding author contact information, E-mail the corresponding author, Xie Quan, Yazhi Zhao, Shuo Chen Journal of H azardous Materials Volume 166, Issue 1, 15 July 2009, Pages 547‰ÛÒ552 2009 This research focused on immersion method synthesis of visible light active salicylic acid (SA)-modified TiO2 nanotube array electrode and its photoelectrocatalytic (PEC) activity. The SA-modified TiO2 nanotube array electrode was synthesized by immersing in SA solution with an anodized TiO2 nanotube array electrode. Scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), UV‰ÛÒvis diffuse reflectance spectrum (DRS), and Surface photovoltage (SPV) were used to characterize this electrode. It was found that SA-modified TiO2 nanotube array electrode absorbed well into visible region and exhibited enhanced visible light PEC activity on the degradation of p-nitrophenol (PNP). The degradation efficiencies increased from 63 to 100% under UV light, and 79‰ÛÒ100% under visible light (ëÈ > 400 nm), compared with TiO2 nanotube array electrode. The enhanced PEC activity of SA-modified TiO2 nanotube array electrode was attributed to the amount of surface hydroxyl groups introduced by SA-modification and the extension of absorption wavelength range. http://www.sciencedirect.com/science/article/pii/S0304389408017470 TiO2 nanotube; Salicylic acid; Photoelectrocatalysis; Nitrophenol; Modification
3/16/2015 9: 05:52 * Effect of Fe modification on H2S sensing properties of rheotaxially grown and thermally oxidized SnO2 thin films Niranjan S. R amgir, N. Datta, Suresh Kumar, S. Kailasaganapathi, U.V. Patil, N. Karmakar, M. Kaur, A.K. Debnath, D.C. Kothari, D.K. Aswal, S.K. Gupta Materials Chemistry and Physics, 2015 Mar-15 Gas sensing properties of pure and Fe modified SnO2 thin films deposited by rheotaxial grown and thermal oxidation (RGTO) method have been investigated. Modification of SnO2 surface with Fe results in an improved and selective response towards H2S. Sensor films containing 0.64 at % Fe exhibited a sensor response of 14.5 towards 10 ppm of H2S at 225 å¡C with a response and recovery time of 90 and 98 s, respectively. Long term stability measurements indicate that the sensor response is stable over a measured period of 35 days. X-ray photoelectron spectroscopy analysis indicates that Fe exists in the form of Fe3O4 over the SnO2 sensor surface. An improved response towards H2S is attributed to the formation of low band gap FeS upon interaction of Fe3O4 with the H2S. A gas sensing mechanism has been proposed using the results of sensing characteristics, x-ray photoelectron spectroscopy and work function measurements. http://www.sciencedirect.com/science/article/pii/S0254058415001571 Thin films; Vacuum deposition; Chemisorption; Surface properties
6/30/2015 10:20:17 KP020 Negative resistance in Cu2O/In2S3 heterostructure R. Jayakrishn an Materials Chemistry and Physics, 2015 2015 A semiconductor hetero-structure exhibiting photovoltaic effect was grown by a combination of sequential ionic layer adsorption reaction and chemical spray pyrolysis technique. The forward current‰ÛÒvoltage characteristic of the device showed a dynamic negative resistance region. It was observed that the onset of the dynamic negative resistance can be tuned by the illumination intensity of the incident light. Low temperature electrical studies of the device showed the presence of shallow states at ‰ö¼80 meV and ‰ö¼15 meV in the band structure. Work function measurement using Kelvin Probe proved the presence of inverted bands in this hetero structure. Shallow states trapped within these bands may be responsible for the negative resistance exhibited by the hetero-structure. http://www.sciencedirect.com/science/article/pii/S025405841530167X Thin films; Nanostructures; Semiconductors; Metals; Multilayer
1/13/2014 14:53:33 UHV Solution-Processed LiF for Work Function Tuning in Electrode Bilayers Taner Aytun, Ayse Turak, Iain Baikie, Grzegorz Halek, and Cleva W. Ow-Yan Nano Lett., 2 012, 12 (1), pp 39‰ÛÒ44 2012 Although ambient processing is the key to low-cost organic solar cell production, high-vacuum thermal evaporation of LiF is often a limiting step, motivating the exploration of solution processing of LiF as an alternative electrode interlayer. Submonolayer films are realized with the assistance of polymeric micelle reactors that enable LiF particle deposition with controlled nanoscale surface coverage. Scanning Kelvin probe reveals a work function tunable with nanoparticle coverage with higher values than that of bare indium tin oxide (ITO). http://pubs.acs.org/doi/abs/10.1021/nl202838a surface work function tuning, organic solar cells, LiF, depolarization UHV 020
1/13/2014 14:28:17 SPV Stability Study of Alkyl Monolayers Directly Attached to Si (111) Surface for Solar Cells Application Mohd Adib I brahim et al., Nicholas Alderman et al. Latest Trends in Renewable Energy and Environmental Informatics (2013) 2013 * http://www.wseas.org/multimedia/books/2013/Malaysia/RESEN.pdf surface recombination, chemical passivation, 1-decene, hydrosilylation, alkyl monolayers
1/13/2014 14:31:05 SKP 5050 + S PS 050 Surface photovoltage characterization of organic photovoltaic devices Yun-Ju Lee, J ian Wang, and Julia W. P. Hsu Applied Physics Letters 103, 173302 (2013) 2013 Surface photovoltage response in bulk heterojunction organic solar cells is determined using a Kelvin probe with variable illumination intensity and wavelength. The effect of devicearchitecture, carrier transport layers, donor:acceptor combinations, and device processing conditions are studied. We observe a positive (negative) surface photovoltage response, corresponding to efficient accumulation of electrons (holes) at the top electrode in conventional (inverted) devices. The linear relationship between surface photovoltage and log(intensity) and the agreement with open circuit voltage indicate that surface photovoltage magnitude quantifies the separation of photogenerated carriers in organic solar cells at open circuit condition. http://scitation.aip.org/content/aip/journal/apl/103/17/10.1063/1.4827104 surface photovoltage, bulk heterojunction, organic solar cells, carrier transport layers, donor/acceptor combinations
1/13/2014 14:18:48 SKP 5050 Determination of surface recombination velocities of organic monolayers on silicon through Kelvin probe Nicholas Ald erman, Mohd Adib Ibrahim, Lefteris Danos, Martin C. Grossel, and Tom Markvart Appl. Phys. Lett. 103, 081603 (2013) 2013 We report the determination of the surface recombination velocity of electron-hole pairs forsilicon samples passivated with organic monolayers using the Kelvin probe. The recombinationvelocity was determined from the surface photovoltage and incident photon flux. By scanning of the Kelvin probe tip over the sample, the change in surface recombination velocity can bemeasured allowing recombination lifetime mapping. Organic monolayers with different chain lengths and exhibiting various recombination lifetimes were synthesized through a two-step chlorination-alkylation technique. The estimated recombination lifetimes were compared against those obtained from an industrial standard technique and were found to be in good agreement. http://scitation.aip.org/content/aip/journal/apl/103/8/10.1063/1.4818768 surface passivation, semiconductor surfaces, photons, silicon, velocity measurement, monolayers, passivation, carrier generation, illumination, surface measurements
11/05/14 10:05 SKP5050 p-Doped Multiwall Carbon Nanotube/Perylene Diimide Derivative Photoelectrochemical Cells for Photocurrent Generation Anna Troeger, Marc Ledendecker, Johannes T. Margraf, Vito Sgobba, Dirk M. Guldi, Benito F. Vieweg, Erdmann Spiecker, Sabin-Lucian Suraru andFrank W̼rthner Advanced Energy Materials (2:5), 2012, pp.536-540. May-12 A perylened iimide (PDI) derivative bearing four chlorine substituents in the bay area is deposited together with pristine multiwall carbon nanotubes (MWNTs) and/or Nafion p-doped MWNTs (p-MWNTs) onto indium tin oxide (ITO) solid substrates by means of air-brushing. The resulting photoanodes are studied in photoelectrochemical cells and reveal highest photocurrent efficiencies when PDI and p-MWNT are combined as photoactive materials, indicating the beneficial effect of Nafion. http://onlinelibrary.wiley.com/doi/10.1002/aenm.201100710/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false solar cells;carbon nanotubes;perylene diimide;heterojunctions;photocurrent generation
1/13/2014 14:51:52 SKP + RHC The Relationship of Surface Roughness and Work Function of Pure Silver by Numerical Modeling Ye Wan, Yan bo Li, Qing Wang, Ke Zhang, Yuhou Wu Int. J. Electro chem. Sci., 7 (2012) 5204 - 5216 2012 * http://www.electrochemsci.org/list12.htm silver, work function, surface roughness, modeling study
1/13/2014 14:41:36 SKP Interactive Effect of Hysteresis and Surface Chemistry on Gated Silicon Nanowire Gas Sensors Yair Paska and Hossam Haick ACS Appl. Mater. Interfaces, 2012, 4 (5), pp 2604‰ÛÒ2617 2012 Gated silicon nanowire gas sensors have emerged as promising devices for chemical and biological sensing applications. Nevertheless, the performance of these devices is usually accompanied by a ‰ÛÏhysteresis‰Û phenomenon that limits their performance under real-world conditions. In this paper, we use a series of systematically changed trichlorosilane-based organic monolayers to study the interactive effect of hysteresis and surface chemistry on gated silicon nanowire gas sensors. The results show that the density of the exposed or unpassivated Si‰ÛÒOH groups (trap states) on the silicon nanowire surface play by far a crucial effect on the hysteresis characteristics of the gated silicon nanowire sensors, relative to the effect of hydrophobicity or molecular density of the organic monolayer. Based on these findings, we provide a tentative model-based understanding of (i) the relation between the adsorbed organic molecules, the hysteresis, and the related fundamental parameters of gated silicon nanowire characteristics and of (ii) the relation between the hysteresis drift and possible screening effect on gated silicon nanowire gas sensors upon exposure to different analytes at real-world conditions. The findings reported in this paper could be considered as a launching pad for extending the use of the gated silicon nanowire gas sensors for discriminations between polar and nonpolar analytes in complex, real-world gas mixtures. http://pubs.acs.org/doi/abs/10.1021/am300288z silicon, nanowire, transistor, sensor,hysteresis
1/13/2014 14:29:58 KP 020 Effect of chain length on the sensing of volatile organic compounds by means of silicon nanowires Bin Wang and Hossam Haick ACS Appl. Mater. Interfaces, 2013, 5 (12), pp 5748-5756 2013 Molecularly modified silicon nanowire field effect transistors (SiNW FETs) are starting to appear as promising devices for sensing various volatile organic compounds (VOCs). Understanding the connection between the molecular layer structure attached to the SiNWs and VOCs is essential for the design of high performance sensors. Here, we explore the chain length influence of molecular layers on the sensing performance to polar and nonpolar VOCs. SiNW FETs were functionalized with molecular layers that have similar end (methyl) group and amide bridge bond, but differ in their alkyl chain lengths. The resulting devices were then exposed to polar and nonpolar VOCs in various concentrations. Our results showed that the sensing response to changing the threshold voltage (ëÓVth) and changing the relative hole mobility (ëÓë¼h/ë¼h-a) have a proportional relationship to the VOC concentration. On exposure to a specific VOC concentration, ëÓVth response increased with the chain length of the molecular modification. In contrast, ëÓë¼h/ë¼h-a did not exhibit any obvious reliance on the chain length of the molecular layer. Analysis of the responses with an electrostatic-based model suggests that the sensor response in ëÓVth is dependent on the VOC concentration, VOC vapor pressure, VOC‰ÛÒmolecular layer binding energy, and VOC adsorption-induced dipole moment changes of molecular layer. http://pubs.acs.org/doi/abs/10.1021/am401265z silicon nanowire, field effect transistor, vapor sensor, dipole, volatile organic compound
1/13/2014 14:26:01 SKP Effect of Functional Groups on the Sensing Properties of Silicon Nanowires toward Volatile Compounds Bin Wang and Hossam Haick ACS Appl. Mater. Interfaces, 2013, 5 (6), pp 2289‰ÛÒ2299 2013 Molecular layers attached to a silicon nanowire field effect transistor (SiNW FET) can serve as antennas for signal transduction of volatile organic compounds (VOCs). Nevertheless, the mutual relationship between the molecular layers and VOCs is still a puzzle. In the present paper, we explore the effect of the molecular layer‰Ûªs end (functional) groups on the sensing properties of VOCs. Toward this end, SiNW FETs were modified with tailor-made molecular layers that have the same backbone but differ in their end groups. Changes in the threshold voltage (ëÓVth) and changes in the mobility (ëÓë¼h) were then recorded upon exposure to various VOCs. Model-based analysis indicates that the interaction between molecular layers and VOCs can be classified to three main scenarios: (a) dipole‰ÛÒdipole interaction between the molecular layer and the polar VOCs; (b) induced dipole‰ÛÒdipole interaction between the molecular layers and the nonpolar VOCs; and (c) molecular layer tilt as a result of VOCs diffusion. Based on these scenarios, it is likely that the electron-donating/withdrawing properties of the functional groups control the dipole moment orientation of the adsorbed VOCs and, as a result, determine the direction (or sign) of the ëÓVth. Additionally, it is likely the diffusion of VOCs into the molecular layer, determined by the type of functional groups, is the main reason for the ëÓë¼h responses. The reported findings are expected to provide an efficient way to design chemical sensors that are based on SiNW FETs to nonpolar VOCs, which do not exchange carriers with the molecular layers. http://pubs.acs.org/doi/abs/10.1021/am4004649 silicon nanowire, field effect transistor, sensor, molecular layer, dipole
1/13/2014 14:23:45 SKP 5050 Functioned RGO with PolySchiff base: Multi-Chemical Sensor for TNT, Acidochromic and Electrochromic Properties Lina Ma, Pin g Zhao, Wenjun Wu, Haijun Niu, Jiwei Cai, Yongfu Lian, Xuduo Bai, Wen Wang Polym. Chem., 2013,4, 4746-4754 2013 In this work, we synthesized a conjugated polyschiff base (PSB) from N,N‰Û²-bis(4-aminophenyl)-N,N‰Û²-bis(ë²-naphthyl)-bisphenylenediamine and 2,5-thiophene-dialdehyde throughcondensation polymerization, in which the triphenylamine (TPA) core acted as an electron donor and hole transporting material, subsequently the polymer was directly used to react withgraphene in the presence of an excess of N-methylglycine to produce a highly soluble RGO covalently functionalized with PSB. The composite was fully characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectrometry, thermogravimetric analysis (TGA),photoluminescence (PL) spectroscopy, UV-Vis absorption spectroscopy, cyclic voltammetry(CV), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). A stable, highly efficient charge-transfer configuration was disclosed and confirmed. The work function values of the PSB and RGO‰ÛÒPSB were obtained by Kelvin probe force microscopy (KPFM) measurements. The devices based on RGO‰ÛÒPSB also showed nonvolatile resistive switching behavior. This composite exhibited higher electrochemical catalytic activity for trinitrotoluene (TNT) and showed excellent electrochromic, acidochromic, and photochromic properties. http://pubs.rsc.org/en/Content/ArticleLanding/2013/PY/c3py00641g RGO, polyschiff base, graphene, work functions
11/05/14 10:02 SKP5050+SPV020 The role of sodium surface species on oxygen charge transfer in the Pt/YSZ system Naimah Ibra him, Danai Poulidi, Maria Elena Rivas, Iain D. Baikie, Ian S. Metcalfe Electrochimi ca Acta (76), 2012, pp. 112-119 Aug-12 The role of sodium surface species in the modification of a platinum (Pt) catalyst film supported on 8 mol% yttria-stabilised-zirconia (YSZ) was investigated under a flow of 20 kPa oxygen at 400 å¡C. Cyclic and linear sweep voltammetry were used to investigate the kinetics of the oxygen charge transfer reaction. The Pt/YSZ systems of both ‰Û÷clean‰Ûª and variable-coverage sodium-modified catalyst surfaces were also characterised using SEM, XPS and work function measurements using the Kelvin probe technique. Samples with sodium coverage from 0.5 to 100% were used. It was found that sodium addition modifies the binding energy of oxygen onto the catalyst surface. Cyclic voltammetry experiments showed that higher overpotentials were required for oxygen reduction with increasing sodium coverage. In addition, sodium was found to modify oxygen storage and/or adsorption and diffusion increasing current densities at higher cathodic overpotential. Ex situ XPS measurements showed the presence of sodium hydroxide, carbonate and/or oxide species on the catalyst surface, while the Kelvin probe technique showed a decrease of approximately 250 meV in the work function of samples with more than 50% sodium coverage (compared to a nominally ‰Û÷clean‰Ûª sample). http://www.sciencedirect.com/science/article/pii/S0013468612007906 Pt/YSZ system; Oxygen charge transfer; Sodium surface impurities; Cyclic voltammetry; Kelvin probe
1/13/2014 14:24:57 SKP 5050 Correlation between the Open Circuit Voltage and the Energetics of Organic Bulk Heterojunction Solar Cells Ilja Lange, Ju liane Kniepert, Patrick Pingel, Ines Dumsch, Sybille Allard, Silvia Janietz, Ullrich Scherf, and Dieter Neher J. Phys. Chem. Lett., 2013, 4, pp 3865‰ÛÒ3871 2013 A detailed investigation of the open circuit voltage (VOC) of organic bulk heterojunction solar cells comprising three different donor polymers and two different fullerene-based acceptors is presented. Bias amplified charge extraction (BACE) is combined with Kelvin Probe measurements to derive information on the relevant energetics in the blend. On the example of P3HT:PC70BM the influence of composition and preparation conditions on the relevant transport levels will be shown. Moderate upward shifts of the P3HT HOMO depending on crystallinity are observed, but contrarily to common believe, the dependence of VOC on blend composition and thermal history is found to be largely determined by the change in the PCBM LUMO energy. Following this approach, we quantified the energetic contribution to the VOC in blends with fluorinated polymers or higher adduct fullerenes. http://pubs.acs.org/doi/abs/10.1021/jz401971e polymer solar cells, P3HT, PCPDTBT, PCBM, ICBA, DOS, HOMO, LUMO
1/13/2014 14:42:22 SKP 5050 An Electrochemical Approach for Deposition of Polyfullerene Films on ITO Substrates P. Veerender, S. P. Koiry, P. Jha, Vibha Saxena, A. K. Chauhan, S. Bhattacharya, R. Tewari, D. K. Aswal, and S. K. Gupta Journal of Th e Electrochemical Society, 159 (1) D13-D18 (2012) 2012 We present deposition of uniform polyfullerene films on ITO substrates using a novel electrochemical concept based on the oxidation of C60 dianion (C602‰öÕ) solution. The C602‰öÕ solution was prepared by the electroreduction of the C60solution in dichloromethane and its oxidation at ITO surface was carried out using linear sweep voltammetry (LSV) in the ‰öÕ1 to 0 V range. The electrodeposited films were characterized by various techniques, such as, scanning electron microscopy, atomic force microscopy, Kelvin probe microscopy, high-resolution transmission electron microscopy, UV/Vis and Fourier transform infrared spectroscopy. The morphology of electrodeposited polyfullerene film was found to depend upon numbers of LSV scans used for its preparation. After 100 LSV scans, the films exhibited a globular morphology and were found to make a full coverage of ITO substrate. At higher scans, a second layer of polyfullerene was found to grow in the form of whiskers having length and diameter upto 200 and 0.4 ë¼m, respectively. The energy band gap for polyfullerene whiskers was found to be ‰ö¼0.7 eV. Experimental evidence show that C60 polymerizes in the 1-dimensional ‰ÛÏpearl-structure‰Û via [2+2] cycloaddition reaction. http://jes.ecsdl.org/content/159/1/D13 polyfullerene, electrodeposited films
10/29/2014 9:51:35 SKP5050 Surface work function of indium tin oxide treated using plasma immersion ion implantation Long He, Zho nghang Wu, Zebin Li, Jiaqi Ju, Qiongrong Ou and Rongqing Liang Journal of Ph ysics D: Applied Physics (46:17), 2013, 175306 Apr-13 Oxygen plasma immersion ion implantation (O-PIII) was introduced to modify the surface of indium tin oxide (ITO) thin films. X-ray photoelectron spectroscopy and Kelvin probe were employed to study the surface work function of the treated ITO films. The results showed that the surface work function of ITO can be further enhanced by O-PIII treatment based on an oxygen inductively coupled plasma (O-ICP). The change in surface work function correlated largely with the surface stoichiometry and the high work function should be attributed to the elimination of oxygen vacancies. The surface work function of the modified ITO films showed a rapid decreasing trend with a time-dependent curve immediately after O-ICP and O-PIII treatments. However, a stabler modification effect was achieved by O-PIII. http://iopscience.iop.org/0022-3727/46/17/175306/refs plasma immersion ion implantation, indium tin oxide, photoelectron spectroscopy, Kelvin probe and surface work function
03/11/14 11:11 SKP5050 Improvement in the Lifetime of Planar Organic Photovoltaic Cells through the Introduction of MoO3 into Their Cathode Buffer Layers Linda Cattin 1, Mustapha Morsli 2 and Jean Christian Bern̬de Electronics 2 014, 3, 122-131 24/02/14 Recently, MoO3, which is typically used as an anode buffer layer in organic photovoltaic cells (OPVCs), has also been used as a cathode buffer layer (CBL). Here, we check its efficiency as a CBL using a planar heterojunction based on the CuPc/C60 couple. The CBL is a bi-layer tris-(8-hydroxyquinoline) aluminum (Alq3)/MoO3. We show that the OPVC with MoO3 in its CBL almost immediately exhibits lower efficiency than those using Alq3 alone. Nevertheless, the OPVCs increase their efficiency during the first five to six days of air exposure. We explain this evolution of the efficiency of the OPVCs over time through the variation in the MoO3 work function due to air contamination. By comparison to a classical OPVC using a CBL containing only Alq3, if it is found that the initial efficiency of the latter is higher, this result is no longer the same after one week of exposure to ambient air. Indeed, this result is due to the fact that the lifetime of the cells is significantly increased by the presence of MoO3 in the CBL. http://www.mdpi.com/2079-9292/3/1/122/pdf planar organic photovoltaic cells; cathode buffer layer; molybdenum oxide; lifetime; air contamination; work function
11/04/14 14:07 SKP5050 Trap free space charge limited conduction and high mobility in cobalt phthalocyanine - iron phthalocyanine composite thin films Arvind Kuma r, Ajay Singh, S. Samanta, R. Prasad, A. K. Debnath, D. K. Aswal and S. K. Gupta Solid State Phenomena (209), 2013, pp. 52-56. Nov-13 Charge transport of pure and composite thin films (20 nm thickness) of cobalt phthalocyanine (CoPc) and iron phthalocyanine (FePc) grown by molecular beam epitaxy has been investigated in the temperature range of 300 K-25 K. Composite films with optimum composition showed very high mobility of 110 cm2V-1s-1 at room temperature. X-ray diffraction and UV-Vis studies showed that the films were well oriented with planar co-facial structure. The current density-voltage (J-V) characteristics of composite films showed trap free space charge limited conduction (SCLC) while individual phthalocyanine films showed SCLC with exponential distribution of traps. Several factors such as effect of substrate, very small thickness and effect of mixing two phthalocyanines are responsible for the very high mobility observed in present study. http://www.scientific.net/SSP.209.52 Phthalocyanine, space charge limited current, thin films
01/06/15 11:11 APS02 Ambient pressure photoemission spectroscopy of metal surfaces Iain D. Baikie, Angela C. Grain, James Sutherland and Jamie Law Applied Surface Science (323), 2014, pp. 45-53. Dec-14 We describe a novel photoemission technique utilizing a traditional Kelvin probe as a detector of electrons/atmospheric ions ejected from metallic surfaces (Au, Ag, Cu, Fe, Ni, Ti, Zn, Al) illuminated by a deep ultra-violet (DUV) source under ambient pressure. To surmount the limitation of electron scattering in air the incident photon energy is rastered rather than applying a variable retarding electric field as is used with UPS. This arrangement can be applied in several operational modes: using the DUV source to determine the photoemission threshold (ë¦) with 30‰ÛÒ50 meV resolution and also the Kelvin probe, under dark conditions, to measure contact potential difference (CPD) between the Kelvin probe tip and the metallic sample with an accuracy of 1‰ÛÒ3 meV. We have studied the relationship between the photoelectric threshold and CPD of metal surfaces cleaned in ambient conditions. Inclusion of a second spectroscopic visible source was used to confirm a semiconducting oxide, possibly Cu2O, via surface photovoltage measurements with the KP. This dual detection system can be easily extended to controlled gas conditions, relative humidity control and sample heating/cooling. http://www.sciencedirect.com/science/article/pii/S0169433214019370 Photoemission spectroscopy, SPV, SPS, metal oxides, work function, Cu2O
1/13/2014 14:46:21 KP 020 Calcium niobate nanosheets as a novel electron transport material for solution-processed multi-junction polymer solar cells Lilian Chang, Michael A. Holmes, Mollie Waller, Frank E. Osterloh and Adam J. MoulÌ© J. Mater Chem., 2012,22, 20443-20450 2012 Solution-processed tandem polymer solar cells are demonstrated using stacked perovskite, (TBA,H)Ca2Nb3O10 (CNO), semiconductor nanosheets as an electron transport layer (ETL) within the recombination layers. Two poly(3-hexylthiophene):(6,6)-phenyl-C61-butyric acid methyl ester, P3HT:PCBM, sub-cells connected in series via a CNO‰ÛÒpoly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), Pedot:PSS, recombination layer provide a Vocof 1.02 V. The Voc is less than double that of a single junction due to leakage (dark) current. When TiOx is used as an additional hole-blocking layer within the recombination stack, the Voc is improved to 1.16 V. Although further optimization of the CNO-layer is still required, the use of CNO nanosheets within the recombination stack shows clear advantages. In addition to electronextraction from photoactive layers, the presence of defect states in the CNO nanosheets with trapped electrons facilitates the recombination of holes from Pedot:PSS, enhancing the function of the recombination stack. The robust CNO-layer can be spin-coated on top of a P3HT:PCBM bulk-heterojunction photoactive layer and is stable toward subsequent processing and heat-treatment. http://pubs.rsc.org/en/content/articlelanding/2012/jm/c2jm33351a perovskite, P3HT:PCBM, PEDOT:PSS
3/13/2015 9: 06:54 KP020 Optical properties and conductivity of PEDOT:PSS films treated by polyethylenimine solution for organic solar cells Zaifang Li, Fe i Qin, Tiefeng Liu, Ru Ge, Wei Meng, Jinhui Tong, Sixing Xiong and Yinhua Zhou Organic Electronics, 2015 Mar-15 We report on conductivity and optical property of three different types of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films [pristine PH1000 film (PH1000-p), with 5 wt.% ethylene glycol additive (PH1000-EG) and with sulfuric acid post-treatment (PH1000-SA)] before and after polyethylenimine (PEI) treatment. The PEI is found to decrease the conductivity of all the PEDOT:PSS films. The processing solvent of 2-methoxyethanol is found to significantly enhance the conductivity of PH1000-p from 1.1 up to 744 S/cm while the processing solvent of isopropanol or water does not change the conductivity of PH1000-p much. As for the optical properties, the PEI treatment slightly changes the transmittance and reflectance of PH1000-p and PH1000-EG films, while the PEI leads to an substantial increase of the absorptance in the spectral region of 400‰ÛÒ1100 nm of the PH1000-SA films. Though the optical property and conductivity of the three different types of PEDOT:PSS films vary with the PEI treatment, the treated PEDOT:PSS films exhibit similar low work function. We demonstrate solar cells with a simple device structure of glass/low-WF PEDOT:PSS/P3HT:ICBA/high-WF PEDOT:PSS cells that exhibit good performance with open-circuit voltage of 0.82 V and fill factor up to 0.62 under 100 mW/cm2 white light illumination. http://www.sciencedirect.com/science/article/pii/S1566119915001019 PEDOT:PSS; Polyethylenimine; Conductivity; Optical property; Organic solar cells
1/13/2014 14:28:51 KP 020 High work-function hole transport layers by self-assembly using a fluorinated additive Scott A. Mauger, Jun Li, Ì–zge T̼z̼n Ì–zmen, Andy Y. Yang, Stephan Friedrich, M. Diego Rail, Louise A. Berben and Adam J. MoulÌ© J. Mater. Chem. C, 2013, Advance Article 2013 The hole transport polymer poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) derives many of its favorable properties from a PSS-rich interfacial layer that forms spontaneously during coating. Since PEDOT:PSS is only usable as a blend it is not possible to study PEDOT:PSS without this interfacial layer. Through the use of the self-doped polymer sulfonated poly(thiophene-3-[2-(2-methoxyethoxy) ethoxy]-2,5-diyl) (S-P3MEET) and a polyfluorinated ionomer (PFI) it is possible to compare transparent conducting organic films with and without interfacial layers and to understand their function. Using neutron reflectometry, we show that PFI preferentially segregates at the top surface of the film during coating and forms a thermally-stable surface layer. Because of this distribution we find that even small amounts of PFI increase the electron work function of the hole transport layer. We also find that annealing at 150 å¡C and above reduces the work function compared to samples heated at lower temperatures. Using near edge X-ray absorption fine structure spectroscopy and gas chromatography we show that this reduction in work function is due to S-P3MEET being doped by PFI. Organic photovoltaic devices with S-P3MEET/PFI hole transport layers yield higher power conversion efficiency than devices with pure S-P3MEET or PEDOT:PSS hole transport layers. Additionally, devices with a doped interface layer of S-P3MEET/PFI show superior performance to those with un-doped S-P3MEET. http://pubs.rsc.org/en/content/articlelanding/2013/tc/c3tc30973h PEDOT:PSS, S-P3MEET, PFI, transparent conducting organic films
1/13/2014 14:38:51 SKP 5050 Improvement of Interfacial Contacts for New Small-Molecule Bulk-Heterojunction Organic Photovoltaics Andres Garcia, Gregory C. Welch, Erin L. Ratcliff, David S. Ginley, Guillermo C. Bazan, Dana C. Olson Advanced Materials, Volume 24, Issue 39, pages 5368‰ÛÒ5373, October 9, 2012 2012 The influence of protonation reactions between poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and a thiadiazolo[3,4-c]pyridine small-molecule donor are reported; these result in poor solar-cell performance due to a barrier for charge extraction. The use of a NiOx contact eliminates such deleterious chemical interactions and results in substantial improvements in open-circuit voltage, fill factor, and an increased power conversion efficiency from 2.3% to 5.1%. http://onlinelibrary.wiley.com/doi/10.1002/adma.201200963/full PEDOT:PSS, organic solar cells, small molecules, hole transport layer, interfacial chemistry, bulk-heterojunction organic photovoltaics
1/13/2014 14:46:54 KP 020 Directional dependence of electron blocking in PEDOT:PSS Scott A. Mauger, Lilian Chang, Christopher W. Rochester, Adam J. MoulÌ© Organic Electronics, Volume 13, Issue 11, November 2012, Pages 2747‰ÛÒ2756 2012 The directional dependence of electron blocking by poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is investigated in organic photovoltaic devices. In a conventional OPV architecture we find that a doped interlayer forms between poly(3-hexylthiophene) (P3HT) and the PSS-rich top layer of spin-coated PEDOT:PSS films. In an inverted OPV architecture, we find no mixing between PEDOT:PSS and P3HT, which is due to the lower concentration of PSS in bulk PEDOT:PSS than is found in the PSS-rich top layer. Through electrical measurements of conventional and inverted photovoltaic devices we show that the interlayer is necessary for PEDOT:PSS to be electron blocking. This result implies that PEDOT:PSS is not intrinsically electron blocking and that its directional anisotropy must be considered when comparing the advantages and disadvantages of conventional and inverted architecture photovoltaic devices. http://www.sciencedirect.com/science/article/pii/S1566119912003771 PEDOT:PSS, electron blocking, organic photovoltaics, inverted architecture
11/04/14 15:28 SKP5050 Investigation of P3HT/n-Si heterojunction using surface photovoltage spectroscopy Yongchang Sang, Aimin Liu, Weifeng Liu and Dawei Kang Vacuum (86: 12), 2012, pp. 2158 - 2161 Jul-12 Surface photovoltage spectroscopy (SPS) was used to investigate the interactions of the interface between regioregular poly(3-hexylthiophene) (P3HT) and n-type single crystalline silicon. The SPS responses of silicon and the P3HT/n-Si heterojunction caused by band to band transition of silicon are 30 mV and 160 mV respectively. The band-bending in the silicon side of the P3HT/n-Si structure is larger than that of bare n-Si. The density of the interface states of the P3HT/n-Si heterojunction increased significantly after the deposition of P3HT. Based on the contact potential difference (CPD) transient results, charge transport and separation processes are fast in the silicon substrate and slow in the P3HT layer respectively. http://www.sciencedirect.com/science/article/pii/S0042207X12002333 P3HT/n-Si heterojunction, surface photovoltage spectroscopy, charge separation and transport
1/13/2014 14:16:34 SKP 5050 Comprehensive picture of p-type doping of P3HT with the molecular acceptor F4TCNQ P. Pingel and D. Neher Physical Review B 87, 115209 (2013) 2013 By means of optical spectroscopy, Kelvin probe, and conductivity measurements, we study the p-type doping of the donor polymer poly(3-hexylthiophene), P3HT, with the molecular acceptor tetrafluorotetracyanoquinodimethane, F4TCNQ, covering a broad range of molar doping ratios from the ppm to the percent regime. Thorough quantitative analysis of the specific near-infrared absorption bands of ionized F4TCNQ reveals that almost every F4TCNQ dopant undergoes integer charge transfer with a P3HT site. However, only about 5% of these charge carrier pairs are found to dissociate and contribute a free hole for electrical conduction. The nonlinear behavior of the conductivity on doping ratio is rationalized by a numerical mobility model that accounts for the broadening of the energetic distribution of transport sites by the Coulomb potentials of ionized F4TCNQ dopants. http://prb.aps.org/abstract/PRB/v87/i11/e115209 P3HT, F4TCNQ
11/04/14 15:49 SKP5050 Transparent high-surface-work-function Al-doped CdO electrodes obtained by rf magnetron sputtering with oxygen flow Wei-Min Ch o, Guan-Ru He, Ting-Hong Su and Yow-Jon Lin Applied Surface Science (258:10), 2012, pp. 4632-4636. Mar-12 The surface work function of transparent conducting oxides is a critical parameter influencing device efficiency by controlling charge transport across interfaces. In this study, Al-doped CdO films were deposited on glass substrates by rf magnetron sputtering with and without oxygen flow. For Al-doped CdO films deposited with (without) oxygen flow, we measure the high (low) surface work function close to 5.4 (4.6) eV. Our results suggest a method for fabricating Al-doped CdO electrodes with large, tunable work functions that could be relevant in designing electrodes for improving the performance of optoelectronic and electronic devices. http://www.sciencedirect.com/science/article/pii/S0169433212000554 oxide, thin films, surfaces, optical properties, work function
10/28/2014 16:45:59 SKP5050 High voltage in hole conductor free organo metal halide perovskite solar cells Alexander Dymshits, Amit Rotem and Lioz Etgar Journal of Materials Chemistry A Oct-14 Organo metal halide perovskite has attracted much attention recently due to distinctive properties that make it especially useful in photovoltaic solar cells. In this work we demonstrate high open circuit voltage of 1.35V using Al2O3/CH3NH3PbBr3 perovskite solar cells without a hole conductor. The contact potential difference under light measured by surface photovoltage spectroscopy for CH3NH3PbBr3 was more than twice than that for CH3NH3PbI3, which results with smaller surface potential for the Al2O3/CH3NH3PbBr3 cells. Incident modulated photovoltage spectroscopy shows a longer recombination lifetime for the Al2O3/CH3NH3PbBr3 cells than for the TiO2/CH3NH3PbI3 cells or for the TiO2/CH3NH3PbBr3 cells, further supporting the high open circuit voltage. The possibility to gain high open circuit voltage even without a hole transport material in perovskite solar cells shows that the perovskite/metal oxide interface has a major effect on the open circuit voltage in perovskite based solar cells. http://pubs.rsc.org/en/content/articlelanding/2014/ta/c4ta05613b#!divAbstract organo metal halide perovskite, photovoltaic solar cells, high open circuit voltage
11/04/14 21:27 SKP5050 Nanocrystal V2O5 thin film as hole-extraction layer in normal architecture organic solar cells Hai-Qiao Wang, Ning Li, Nusret Sena Guldal and Christoph J. Brabec Organic Electronics (13:12), 2012, pp. 3014-3021 Dec-12 Nanocrystal V2O5 dispersion processed thin films are introduced as efficient hole extraction interlayer in normal architecture P3HT:PCBM solar cells. Both thin and rather thick interlayers are studied and demonstrated to work properly in organic photovoltaic. Nanocrystal V2O5V2O5 layers effectively block electrons and effectively extract holes at the ITO anode. Very constant and high VOC (above 0.56 V) are easily achieved. Comparable JSC and PCE are demonstrated for nanocrystal dispersion-processed devices when compared with amorphous sol‰ÛÒgel processed devices. The excellent functionality of nanocrystal V2O5 interlayers in Si-PCPDTBT:PCBM devices further demonstrates the broad application potential of this material class for photovoltaic applications. http://www.sciencedirect.com/science/article/pii/S1566119912003801 Organic solar cell, Vanadium oxide; Nanocrystal, Electrode buffer layer
03/11/14 11:14 UHV020 Characterization of doped PEDOT: PSS and its influence on the performance and degradation of organic solar cells Vinamrita Si ngh1, Swati Arora2, Manoj Arora3, Vishal Sharma1,4 and R P Tandon1 Semicond. Sci. Technol. 05/03/13 Paper The present work is a detailed study of the optical, morphological and electrical properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS, films doped with ethylene glycol (EG) and multi-walled carbon nanotubes (MWCNT). The conductivity of PEDOT:PSS films doped with EG and MWCNT is higher than pristine PEDOT:PSS film. The optical transparency of PEDOT:PSS film decreases insignificantly after addition of MWCNT and EG. The films were further studied using atomic force microscopy, x-ray diffraction, Raman spectroscopy and Kelvin probe work function measurement, after which films of PEDOT:PSS with EG and MWCNT were optimized for the fabrication of solar cells. The optimized film was used as a hole extracting layer in a typical ITO/PEDOT:PSS/P3HT:PCBM/Al solar cell. The suitable concentration for an optimized film was found to be 4% MWCNT and 1:4 ratio of EG to PEDOT:PSS. The performance of the device with doped PEDOT:PSS was found to improve in terms of short circuit current density (JSC) and efficiency (ëá). The solar cell with a doped PEDOT:PSS layer showed higher JSC and ëá due to the increase in the interchains among PEDOT chains along with the introduction of MWCNT channels in PEDOT:PSS matrix. The degradation behavior of the cells was studied and it was found that both pristine and doped PEDOT:PSS cells showed similar trends of degradation. The performance degradation with time was also studied under variable environmental conditions, which showed different aging rates for the two devices. http://iopscience.iop.org/0268-1242/29/4/045020 organic solar cell, degradation, hole extracting layer, carbon nanotubes
11/05/14 09:12 SKP5050 MoO3/CuI hybrid buffer layer for the optimization of organic solar cells based on a donor‰ÛÒacceptor triphenylamine Jean Christian Bern̬de, Linda Cattin, Mohammed Makha, Victorien Jeux, Philippe Leriche, Jean Roncali, Vincent Froger, Mustapha Morsli, Mohammed Addou Solar Energy Materials and Solar Cells (110), 2013, pp.107-114 Mar-13 We investigate the effect of anode buffer layers (ABLs) on the performances of multi-layer heterojunction solar cells with thienylenevinylene‰ÛÒtriphenylamine with peripheral dicyanovinylene groups (thCV‰ÛÒTPA) as donor material and fullerene C60 as acceptor. The deposition of a CuI layer between the ITO anode and the electron donor significantly improves the short-circuit current density (Jsc) and fill factor (FF) but reduces the open-circuit voltage (Voc). On the other hand, a MoO3 buffer layer increases the Voc but leads to limited Jsc and FF values, thus reducing power conversion efficiency (PCE). In this context, we show that the use of a hybrid anode buffer layer MoO3/CuI leads to a considerable improvement of the cells performances and a PCE of 2.50% has been achieved. These results are discussed on the basis of the dual function of MoO3 and CuI. While both of them reduce the hole injection barrier, CuI improves the conductivity of the organic film through an improvement of molecular order while MoO3 prevents leakage current through the diode. Finally the results of a cursory study of the ageing process provide further support to this interpretation of the effects of the various buffer layers. http://www.sciencedirect.com/science/article/pii/S0927024812005338 Organic photovoltaics; Thin film; Small molecules; Copper iodide; Anode buffer layer
1/13/2014 14:26:39 SKP 5050 Highly-Tunable Nickel Cobalt Oxide as a Low-Temperature P-Type Contact in Organic Photovoltaic Devices Paul F. Ndio ne, Andres Garcia, N. Edwin Widjonarko, Ajaya K. Sigdel, K. Xerxes Steirer, Dana C. Olson, Philip A. Parilla, David S. Ginley, Neal R. Armstong, Robin E. Richards, Erin L. Ratcliff, Joseph J. Berry Advanced Energy Materials, Volume 3, Issue 4, pages 524‰ÛÒ531, April, 2013 2013 We report on the investigation of nickel cobalt oxide (NixCo3‰öÕxO4) thin films grown by pulsed laser deposition as hole-transport interlayers (HTL) in organic photovoltaic (OPV) devices. Films of 7 nm thickness were grown under various oxygen deposition pressures (pO2) in the range of 2‰ÛÒ200 mTorr. We explore both bulk and surface properties of these thin films. The workfunction (ì¥) for each of the films was statistically similar (‰ö¼4.7 eV), regardless of pO2. There was not a strong dependence of the power conversion efficiency (ëá) on the conductivities of the HTLs varying between 0.009 - 10 S/cm. The observed differences in OPV efficiencies (ranging from 1.16 to 2.46%) were correlated to the near surface chemical composition of the NixCo3‰öÕxO4 HTL, as observed by differences in the relative surface hydroxyl concentration. The critical role of the near-surface composition of the HTL at the HTL/organic interface was further explored by modifying the hydroxyl concentration using an oxygen plasma treatment. This treatment mitigated the impact of surface hydroxyl coverage, demonstrating either identical or increased values for ì¥ and ëá, regardless of initial pO2 in the creation of the NixCo3‰öÕxO4 HTL. To further explore this we also employed a phosphonic acid surface modification agent on the HTL, increasing ì¥ to 5.2 eV producing the best ëá value of 3.4%, equivalent to the PEDOT:PSS control devices. These results indicate that nickel cobalt oxide is a promising p-type oxide for carrier-selective interlayers in organic solar cells; however, for this to be fully realized the specific surface chemistry at the oxide/polymer interface must be controlled to increase ì¥ and optimize device performance. http://onlinelibrary.wiley.com/doi/10.1002/aenm.201200742/full organic photovoltaics, nickel cobalt oxide, hole transport layer, hydroxyls
11/04/14 14:52 SKP5050 Ultraviolet-ill uminated fluoropolymer indium-tin-oxide buffer layers for improved power conversion in organic photovoltaics Bonan Kang, L. W. Tan and S. R. P. Silva Organic Electronics (10:6), 2009, pp. 1178-1181. Sep-09 We demonstrate that the charge carrier extraction in double heterojunction organic photovoltaic(OPV) devices can be enhanced by inserting an UV-illuminated fluoropolymer polytetrafluoroethylene(PTFE) layer between indium‰ÛÒtin-oxide and the thermal evaporated copper‰ÛÒphthalocyanine(CuPc)/buckyball(C60) organic active layers. In this work, we show that the anode work function influences the photocarrier collection characteristics, where the short-circuit current and open-circuit voltage increase from 1.6 to 4.8 mA/cm2 and 0.41 to 0.48 V, respectively after the buffer layer insertion associated primary with the barrier decrease in the ITO/CuPc interface. This result shows the potential of UV-illuminated PTFE as a low-cost stable buffer layer for OPV devices. http://www.sciencedirect.com/science/article/pii/S1566119909001335 organic photovoltaic, fluoropolymer, UV treatment, PTFE
1/13/2014 14:39:53 SKP 5050 Fluorinated copper-phthalocyanine/cobalt-phthalocyaine organic heterojunctions: Charge transport and Kelvin probe studies A. K. Debnath, Arvind Kumar, S. Samanta, R. Prasad, A. Singh, A. K. Chauhan, P. Veerender, S. Singh, S. Basu, D. K. Aswal, and S. K. Gupta Appl. Phys. Lett. 100, 142104 (2012) 2012 Organic heterojunctions comprising of n-type fluorinated copper-phthalocyanine (F16CuPc) and p-type cobalt-phthalocyanine (CoPc) layers were prepared on (001) LaAlO3 substrates. In the entire temperature range of 300‰ÛÒ30‰ÛäK, F16CuPc/CoPc heterojunctions showed an ohmic conduction with three order of magnitude lower resistivity than the individual layers. This indicates formation of a charge accumulation layer at the interface. Kelvin probe studies showed that charge accumulation layer is ‰ö¼10‰Ûänm thick on both the sides of the interface. http://scitation.aip.org/content/aip/journal/apl/100/14/10.1063/1.3699272 organic heterojunctions, charge accumulation layer
1/13/2014 14:55:23 SKP 5050 Reverse rectification behavior of NiPc (p-type)/F16CuPc (n-type) heterojunction Arvind Kumar, Soumen Samanta, Ajay Singh, A. K. Debnath, R. Prasad, D. K. Aswal, and S. K. Gupta AIP Conf. Proc. 1447, pp. 755-756 (2012) 2012 In this paper we present reverse rectification behavior of an organic heterojunction comprising of nickel phthalocyanine (NiPc) and copper-hexadecafluroro-phthalocyanine (F16CuPc) grown by MBE. Using Kelvin Probe we found that charge is accumulated at both side of interface, electrons in F16CuPc and holes in NiPc. The thickness of charge accumulated at the interface is about 20 nm. Based on Kelvin Probe data, mechanism of reverse rectification is explained. http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.4710223 organic heterojunction, reverse rectification
1/13/2014 15:01:30 SKP Investigation of blister formed on coated mild steel using scanning Kelvin Probe Zalilah Sharer Sahir and John Malcolm Sykes Jurnal Teknology, 56, Dis. 2011: 139-154 2011 The degradation of a coated metal in term of the area underneath a blister has been studied after being immersed in 3% sodium chlorida and 3% ammonium chloride solution. Scanning Kelvin probe (SKP) was used to map electrochemical potentials, identifying anodic and cathodic regions underneath a blister and the surrounding coating. For blisters formed on coated panel immersed in sodium chlorida solution, SKP potential map reveals that the blister has formed at a cathode due to alkali but anodes form nearby (not remote). Meanwhile SKP potential map for blister formed on coated panel in 3% ammonium chloride reveals the presence of cathodic regions within the anodic areas. http://www.jurnalteknologi.utm.my/index.php/jurnalteknologi/article/view/906 organic coating, blister
1/13/2014 14:27:12 SKP 5050 Synthesis of azobenzene substituted tripod-shaped bi(p-phenylene)s. Adsorption on gold and CdS quantum-dots surfaces Jesus Hierrez uelo, Rodrigo Rico, MarÌ­a Valpuesta, Amelia DÌ­az, J. Manuel Lopez Romero, Martins Rutkis, Jana Kreigberga, Valdis Kampars, Manuel Algarra Tetrahedron 69 (2013) 3465e3474 2013 We report here the synthesis of several tripod-shaped oligo(p-phenylene)s with legs composed of two phenylene units. Each leg is end-capped with a thioacetate group for adhesion to metallic surfaces. An azobenzene chromophore group is present on the functional arm of the tripod. The key step in the synthesis is the Pd-catalyzed Suzuki cross-coupling reaction of the silicon derivative core molecule with substituted phenyl moieties and azobenzene derivatives. Gold surfaces prepared by thermal evaporation and CdS quantum-dots surfaces were covered by the tripod-shaped molecules. Modified surfaces were characterized by atomic force microscopy (AFM), fluorescence, and Kelvin Probe analyses. http://www.sciencedirect.com/science/article/pii/S0040402013002809 oligo(p-phenylene)s, chromophores, SAMs, surfaces, nanostructures, sensors
1/13/2014 14:45:28 SKP5050 One-step fabrication of crystalline TiO2 nanotubualr arrays and relevant temperature influences Jie Zhang * 2012 TiO2 nanotube arrays fabricated through anodization have attracted significant interest and have been widely investigated due to their great potential for many applications related to the solar energy utilization for, e. g. photoelectrochemical water splitting, degradation of pollutants and solar cells etc. However, despite many efforts, it remains a major challenge to successfully in-situ fabricate crystalline TiO2. TiO2 nanotubes made by room temperature (R. T.) are generally in the amorphous state, which need to be crystallized at elevated temperutures for the photocatalytic activity. However, during crystallization treatment at elevated temperatures, a barrier layer forms between the nanotubular array and the substrate. The barrier layer reduces the electron transfer in photocatalytic processes such as water photoelectrolysis, which in turn reduces the overall water splitting efficiency. The oxide growth from the underlying Ti foil layer may percolate up and make the nanotubes dysfunctional. The primary objective of this thesis is to explore in-situ fabrication of crystalline TiO2 nanotube arrays via anodization. Anodization at different bath temperatures and anodization potentials was investigated and a direct one-step approach for in- situ fabrication of crystalline TiO2 nanotube arrays has been demonstrated. Research was also conducted to investigate relevant issues and elucidate mechanisms involved. https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=61&ca d=rja&ved=0CC8QFjAAODw&url=https%3A%2F%2Fera.library.ualberta.ca% 2Fpubli c%2Fdatastream%2Fget%2Fuuid%3Aa2ca62a6-7266-495d-b48d- fbf1d622a08d%2FDS1&ei=-zaaUdv- B4XL0QWK6oDoAw&usg=AFQjCNEIu9pK30sk7geGKmXdy9glXwuh0w&sig2 =yR3FdJrkdFsjgF4aysDu-g&bvm=bv.46751780,d.bGE Oligo(p-phenylene)s Chromophores SAMs Surfaces Nanostructures Kelvin-Probe
11/04/14 21:42 SKP5050 Pentacene ohmic contact on the transparent conductive oxide films Jian-An Chu, Jian-Jhou Zeng, Kuo-Chen Wu and Yow-Jon Lin Thin Solid Films (519:2), 2010, pp. 868-871. Nov-10 Low-resistance ohmic contacts are essential to improve the performance of pentacene-based electronic and optoelectronic devices. In this study, we reported ohmic contact formation at the indium tin oxide (ITO)/pentacene and indium cerium oxide (ICO)/pentacene interfaces. According to the observed results from current‰ÛÒvoltage and Kelvin probe measurements, we found that the lower contact resistivity of the ICO/pentacene sample than the ITO/pentacene sample may be attributed to the higher surface work function of ICO than ITO. http://www.sciencedirect.com/science/article/pii/S0040609010013064 Ohmic contact; Organic semiconductor; Contact resistance; Oxides
1/13/2014 14:57:17 SKP 5050 Microfabricated Nitrogen-Phosphorus Detector: Chemically Mediated Thermionic Emission Robert J. Simonson, Ryan F. Hess, Matthew Moorman, Timothy Boyle (Sept 2012) * 2012 Many chemical warfare agents and toxic industrial chemicals contain nitrogen and phosphorus atoms. Commercially available benchtop Nitrogen-Phosphorus Detectors (NPDs) for gas chromatographs are highly selective for nitrogen and phosphorus compared to carbon. However, the detection mechanism for these thermionic detectors is poorly understood despite 60 years of use. In addition these detectors require the use of flammable gas and operate at high power. We developed a microfabricated NPD (åµNPD) with similar selectivity that does not require the use of flammable gas and uses relatively low power. Our åµNPD consists of an alkali metal silicate thin film spray coated onto a microhotplate. The silicate thin film is responsible for providing the thermionic emission necessary for analyte detection. We conducted a series of experiments designed to better elucidate the detection mechanism. Our results indicate that surface catalyzed ionization of nitrogen and phosphorus containing analytes is the most likely mechanism. http://prod.sandia.gov/techlib/access-control.cgi/2012/127778.pdf nitrogen-phosphorus detectors
1/13/2014 14:32:48 SPV Planar metal ‰ÛÒinsulator‰ÛÒmetal diodes based on the Nb/Nb2O5/X material system Matthew L. Chin, Prakash Periasamy, et al. J. Vac. Sci. Technol. B 31(5), Sep/Oct 2013 2013 The authors report the performance of various planar metal‰ÛÒinsulator‰ÛÒmetal (MIM) tunneling diodes, which are being investigated for use in rectenna devices for energy harvesting applications. Six cathode materials (M2): Nb, Ag, Cu, Ni, Au, and Pt are studied in conjunction with Nb as the anode (M1) and Nb 2O5 (I) as the dielectric. The cathode materials selections were based on results from a prior rapid-screening study that employed a bent-wire metal cathode point-contact method. Planar devices, to enable analysis using standard MIM diode models, were fabricated with the resultant current density‰ÛÒvoltage data obtained at both room temperature and 77‰ÛäK. The tunnel barrier heights and dielectric properties for these systems were extracted from the modeling results. Nb/Nb2O5/Pt MIM diodes showed the best performance with an asymmetry ratio greater than 7700, a nonlinearity value of 4.7, and a responsivity of 16.9, all at 0.5‰ÛäV and 300‰ÛäK. These results confirm prior rapid-screening efforts and further validate the Nb/Nb2O5/Pt system in particular as a promising MIM architecture due to the low barrier height of the junction. http://scitation.aip.org/content/avs/journal/jvstb/31/5/10.1116/1.4818313 niobium, gold, insulators, tunneling, current density, work functions, electrodes, copper, silver, thin films
1/13/2014 14:39:22 SKP 5050 Sputtered nickel oxide thin film for efficient hole transport layer in polymer‰ÛÒfullerene bulk-heterojunction organic solar cell N. Edwin Widjonarko, Erin L. Ratcliff, Craig L. Perkins, Ajaya K. Sigdel, Andriy Zakutayev, Paul F. Ndione, Dane T. Gillaspie, David S. Ginley, Dana C. Olson, Joseph J. Berry Thin Solid Films, Volume 520, Issue 10, 1 March 2012, Pages 3813‰ÛÒ3818 2012 Bulk-heterojunction (BHJ) organic photovoltaics (OPV) are very promising thin film renewable energy conversion technologies due to low production cost by high-throughput roll-to-roll manufacturing, an expansive list of compatible materials, and flexible device fabrication. An important aspect of OPV device efficiency is good contact engineering. The use of oxide thin films for this application offers increased design flexibility and improved chemical stability. Here we present our investigation of radio frequency magnetron sputtered nickel oxide (NiOx) deposited from oxide targets as an efficient, easily scalable hole transport layer (HTL) with variable work-function, ranging from 4.8 to 5.8 eV. Differences in HTL work-function were not found to result in statistically significant changes in open circuit voltage (Voc) for poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) BHJ device. Ultraviolet photoemission spectroscopy (UPS) characterization of the NiOx film and its interface with the polymer shows Fermi level alignment of the polymer with the NiOx film. UPS of the blend also demonstrates Fermi level alignment of the organic active layer with the HTL, consistent with the lack of correlation between Voc and HTL work-function. Instead, trends in jsc, Voc, and thus overall device performance are related to the surface treatment of the HTL prior to active layer deposition through changes in active layer thickness. http://www.sciencedirect.com/science/article/pii/S0040609011017998 nickel oxide, organic solar cells, hole transport layer, selective interlayer, work function, organic-oxide interface
03/03/15 09:17 APS02, SKP5050, UHVKP020 Near ambient pressure photoemission spectroscopy of metal and semiconductor surfaces Iain D. Baikie, Angela Grain, James Sutherland and Jamie Law Physica status solidi (c), 2015 2015 We describe a novel photoemission technique utilizing a traditional Kelvin probe as a detector of electrons/atmospheric ions ejected from metal and semiconductor surfaces (Al, Ag, Au, Si) illuminated by a Deep Ultra-Violet (DUV) source at ambient pressure. In Constant Final State Yield Spectroscopy (CFSYS) the incident photon energy is rastered rather than applying a variable retarding electric field as in conventional UPS. For both ambient- and near ambient pressure-photoemission spectroscopy (NAP-PES) the CFSYS configuration overcomes the limitation of inelastic electron scattering in air. This arrangement can be applied in several operational modes: using the DUV source to determine the absolute work function (ì¥) of the metal with 50-100 meV resolution and also the Kelvin probe, under dark conditions, to measure Contact Potential Difference (CPD) with an accuracy of 1-3 meV. We show that the metal photoresponse agrees with Fowler theory. We have used CPD and linear extrapolated photoemission measurements to produce an energy level diagram for the native-oxide covered Si. We propose a model of photoemission in air involving atmospheric ions. http://onlinelibrary.wiley.com/doi/10.1002/pssc.201400086/abstract near ambient photoemission spectroscopy; Kelvin probe; CPD; Fowler theory
10/14/2014 16:58:22 SKP5050 with SPS040 One-Step Formation of Crystalline TiO2 Nanotubular Arrays with Intrinsic p-n Junctions Jie Zhang, Xi nhu Tang, Dongyang Li The Journal of Physical Chemistry C Oct-11 It is highly desired to fabricate crystalline TiO2 nanotubes by anodization without subsequent annealing that may result in cracking and the formation of an interfacial barrier between the nanotubular arrays and the substrate, thus improving the structural integrity and corresponding photoelectric properties. In this work, an attempt was made to fabricate crystalline TiO2 nanotubular arrays through anodization in a NH4F-containing glycerol electrolyte at room temperature (RT) and 100 C. It was demonstrated that crystalline nanotubes were successfully fabricated at both RT and 100 C. Photocurrent and surface photovoltage spectra of the nanotubes were measured to investigate their photoinduced charge separation efficiency and semiconductor characteristics. It was interesting to observe that the as-fabricated TiO2 nanotubes at RT consisted of both rutile and anatase, confirmed by SAD of TEM, which showed apparent p-type semiconductor characteristics. The mechanism for the formation of crystallites at RT and the possibility to develop intrinsic nanoscale pn junctions were discussed. However, the nanotubes anodized at 100 C were in the state of anatase, exhibiting n-type semiconductor characteristics. http://pubs.acs.org/doi/abs/10.1021/jp203414q nanotubular array, intrinsic p-n junctions, crystalline TiO2, semiconductor
11/04/14 21:35 SKP5050 Effects of sulfide treatment on electronic transport of graphene/n-type Si Schottky diodes Jian-Jhou Zeng and Yow-Jon Lin Materials Chemistry and Physics (145:2), 2014, pp. 250-254. May-14 The present work reports the fabrication and detailed electrical properties of graphene/n-type Si Schottky diodes with and without sulfide treatment. The graphene/n-type Si Schottky diode without sulfide treatment shows a poor rectifying behavior with an ideality factor (ëá) of 4.2 and high leakage. ëá > 2 implies that the interfacial defects influence the electronic conduction through the device. However, the graphene/n-type Si Schottky diode with sulfide treatment for 5 min shows a good rectifying behavior with ëá of 1.8 and low leakage. Such an improvement indicates that a good passivation is formed at the interface as a result of the reduction of the defect density. These experimental demonstrations suggest that it may be possible to minimize the adverse effects of the interface states to obtain functional devices using sulfide treatment. In addition, the graphene/n-type Si Schottky diode with sulfide treatment for 10 min shows a poor rectifying behavior with ëá of 2.5 and high leakage. Note, a suitable sulfide treatment time is an important issue for improving the device performance. http://www.sciencedirect.com/science/article/pii/S0254058414001084 Nanostructures; Surfaces; Semiconductors; Chemical vapor deposition; Defects; Electrical properties
11/04/14 21:39 SKP5050 Contact potential barriers and characterization of Ag-doped composite TiO2 nanotubes Jingling Lia, Wenzhe Chen, Hualiang Yu, Bo Wu, Wenbo Huang, Mingxiu Wang, Shizhen Huang, Wei Lin, Likun Zhang and Shiping Li Journal of Ph ysics and Chemistry of Solids (75:4), 2014, pp. 505-511. Apr-14 Ag-doping Ti O2 composite nanotubes (Ag-TNTs) were synthesized by alkaline fusion followed by hydrothermal treatment. The microstructure and morphology of the materials were characterized by XRD, TEM, XPS, SPS (surface photovoltage spectroscopy), FISPS (electric field-induced surface photovoltage spectroscopy) and Raman spectroscopy. First-principles calculations based on density-functional theory (DFT) showed the formation of several impurity levels near the top of the valence band in the band gap (Eg) of rutile TiO2 due to Ag doping. A ‰ÛÏdouble junction‰Û is proposed, involving a Schottky junction and p‰ÛÒn junction (denoted as ‰ÛÏAg-p‰ÛÒn junction‰Û) occurring between the Ag particles and the nanotube surface, as well as forming inside TiO2 nanotubes, respectively. The strongly built-in electric field of the junctions promotes the separation of photo-holes and photoelectrons, enhancing the photocatalytic efficiency. XRD results indicated that the composite Ag-TNTs exist as a mixture of anatase and rutile phases. XPS results showed that Ti4+ is the primary state of Ti. Raman spectral analysis of Ag-TNTs revealed the presence of a new peak at 271 cm‰öÕ1. The red-shift of the absorption light wavelength of Ag-TNTs was 0.16 eV (20 nm) due to a considerable narrowing of Eg by the existing impurity levels. http://www.sciencedirect.com/science/article/pii/S002236971300396X Nanostructures; Ab initio calculations; Microstructure; Surface properties; Transport properties
1/13/2014 14:34:03 RHC 020 Lightning rod effect in surface work function of semiconductor nanomaterials Mingshan Xue, Wenfeng Wang, Junfei Ou, Fajun Wang, and Wen Li Appl. Phys. Lett. 102, 243110 (2013) 2013 The inherent correlation between the work function and surface microstructures of semiconductor nanomaterials (SNMs) was investigated. It was found that the work function of SNMs decreased with the increase of the degree of order of SNMs. The well-aligned SNMs corresponded to the lowest work function, which was just as the lightning rod effect being of advantage to the electron transport in SNMs. Such a simple and intuitive analogy to the change trend of work function is of help to enhance the understanding of electron transport of SNMs. http://scitation.aip.org/content/aip/journal/apl/102/24/10.1063/1.4812238 nanorods, annealing, II-VI semiconductors, electronic transport, lightning discharges, surface structure, double layers, capacitors, electrostatics, nanowires
03/01/14 00:32 SKP5050 N-Doped Graphene Field-Effect Transistors with Enhanced Electron Mobility and Air-stability Wentao Xu‰ Û , Tae-Seok Lim‰Û , Hong-Kyu Seo, Sung-Yong Min, Himchan Cho, Min-Ho Park, Young-Hoon Kim, Tae-Woo Lee Small. doi: 1 0.1002/smll.20130376 2014 Although graphene can be easily p-doped by various adsorbates, developing stable n-doped graphene that is very useful for practical device applications is a difficult challenge. We investigated the doping effect of solution-processed (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine (N-DMBI) on chemical-vapor-deposited (CVD) graphene. Strong n-type doping is confirmed by Raman spectroscopy and the electrical transport characteristics of graphene field-effect transistors. The strong n-type doping effect shifts the Dirac point to around -140 V. Appropriate annealing at a low temperature of 80 å¼C enables an enhanced electron mobility of 1150 cm2 V‰öÕ1 s‰öÕ1. The work function and its uniformity on a large scale (1.2 mm Ì— 1.2 mm) of the doped surface are evaluated using ultraviolet photoelectron spectroscopy and Kelvin probe mapping. Stable electrical properties are observed in a device aged in air for more than one month. http://onlinelibrary.wiley.com/doi/10.1002/smll.201303768/full n-type doping;graphene field-effect transistor;carrier mobility;dirac point
1/13/2014 15:07:03 SKP5050 with SPS Highly efficient dye-sensitized solar cells based on nitrogen-doped titania with excellent stability Anders Hagfeldtb, Tingli Maa,‰ö— * 2010 A series of nitrogen-doped and undoped TiO2 nanocrystals was prepared by several simple methods. Needle-like N-doped TiO2 nanocrystals and nanoparticles were obtained from commercial TiO2 powders. Several dye- sensitized solar cells (DSCs) were fabricated based on N-doped and undoped TiO2 electrodes. The N-doped DSCs achieved a high conversion efficiency of 10.1% and 4.8% using an organic electrolyte and an ionic liquid electrolyte, respectively. Systemic investigations were carried out on the properties of N- doped and undoped TiO2 powders, films, and DSCs. The electron transport time and electron lifetime were investigated by intensity-modulated photocurrent and photovoltage spectroscopy (IMPS/IMVS). Moreover, the electron injection of N-doped DSCs was studied by surface photovoltage spectroscopy (SPS). The synergetic effect of higher dye uptake, faster electron transport and higher photovoltage con- tributes to a higher conversion efficiency of N-doped DSCs. The stability test also demonstrated that the photodegradation of the DSCs was not accelerated and the DSC system was stabilized by the introduc- tion of nitrogen into the TiO2 photoelectrode. These results indicate that the N-doped TiO2 nanocrystals prepared by our approach from commercial TiO2 are ideal semiconductor materials for DSCs. https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=59&cad=rja&ved=0CHMQFjAIODI&url=http%3A%2F%2Fwww.researchgate.net%2Fpublicat ion%2F228480169_Highly_efficient_dye-å‰ېsensitized_solar_cells_based_on_nitrogen-å‰ېdoped_titania_with_excellent_stability%2Ffile%2F9fcfd507287923b92e.pdf&ei=7SiaUeiaFqG60QXH44GYAg&usg=AFQjCNHDGxN8TP_BI1szv9KKBt-å‰ې FS_oKMQ&sig2=hQ3_yX223NJgyzydLiJi2g&bvm=bv.46751780,d.bGE N-doped titania Dye-sensitized solar cell Electron transport Photovoltaic performance
1/13/2014 14:38:16 SKP 5050 Impact of electrode roughness on metal-insulator-metal tunnel diodes with atomic layer deposited Al2O3 tunnel barriers Nasir Alimar dani, E. William Cowell, III, John F. Wager, John F. Conley, Jr., David R. Evans, Matthew Chin, Stephen J. Kilpatrick, and Madan Dubey J. Vac. Sci. Technol. A 30, 01A113 (2012) 2012 Metal-insulator-metal (MIM) tunnel diodes on a variety of high and low work function metals with various levels of root-mean-square roughness are fabricated using high quality atomic layer deposited Al2O3as the insulating tunnel barrier. It is found that electrode surface roughness can dominate the current versus voltage characteristics of MIM diodes, even overwhelming the impact of metal work function. Devices with smoother bottom electrodes are found to produce current versus voltage behavior with higher asymmetry and better agreement with Fowler-Nordheim tunneling theory, as well as a greater percentage of functioning devices. http://ieeexplore.ieee.org/iel5/4915548/6007012/06101331.pdf MIM devices, alumina, atomic layer deposition, electrical conductivity, electrodes, insulating materials, surface roughness, tunnel diodes, tunnelling, work function
4/14/2015 11:21:27 SKP5050 MoOx and V 2Ox as hole and electron transport layers through functionalized intercalation in normal and inverted organic optoelectronic devices Xinchen Li, Fengxian Xie, Shaoqing Zhang, Jianhui Hou and Wallace CH Choy Light: Science and Applications (4), 2015 2015 To achieve fabrication and cost competitiveness in organic optoelectronic devices that include organic solar cells (OSCs) and organic light-emitting diodes (OLEDs), it is desirable to have one type of material that can simultaneously function as both the electron and hole transport layers (ETLs and HTLs) of the organic devices in all device architectures (i.e., normal and inverted architectures). We address this issue by proposing and demonstrating Cs-intercalated metal oxides (with various Cs mole ratios) as both the ETL and HTL of an organic optoelectronic device with normal and inverted device architectures. Our results demonstrate that the new approach works well for widely used transition metal oxides of molybdenum oxide (MoOx) and vanadium oxide (V2Ox). Moreover, the Cs-intercalated metal-oxide-based ETL and HTL can be easily formed under the conditions of a room temperature, water-free and solution-based process. These conditions favor practical applications of OSCs and OLEDs. Notably, with the analyses of the Kelvin Probe System, our approach of Cs-intercalated metal oxides with a wide mole ratio range of transition metals (Mo or V)/Cs from 1‰ö¦0 to 1‰ö¦0.75 can offer significant and continuous work function tuning as large as 1.31 eV for functioning as both an ETL and HTL. Consequently, our method of intercalated metal oxides can contribute to the emerging large-scale and low-cost organic optoelectronic devices. http://www.nature.com/lsa/journal/v4/n4/full/lsa201546a.html metal oxides carrier transport layers; normal and inverted device architectures; organic light-emitting diodes; organic solar cells; room-temperature solution process
11/04/14 21:09 SKP5050 High fill factor polymer solar cells comprising a transparent, low temperature solution processed doped metal oxide/metal nanowire composite electrode Tobias Stubhan, Johannes Krantz, Ning Li, Fei Guo, Ivan Litzov, Matthias Steidl, Moses Richter, Gebhard J. Matt, Christoph J. Brabec Solar Energy Materials and Solar Cells (107), 2012, pp. 248-251 Dec-12 In this paper we report on the replacement for the commonly used ITO electrode material by a low temperature solution processed silver nanowire/(doped) metal oxide composite. Devices employing silver nanowires (AgNWs)/buffer layer electrodes with a photoactive layer of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) are showing a comparable performance to the ITO reference cell with fill factors (FF) of over 62% and a power conversion efficiency of ‰ö¼2.7%. Zinc oxide (ZnO) and highly conductive Al doped ZnO (AZO) are used as buffer layer. AgNW devices without a buffer layer have a high open circuit voltage (VOC) but the FF and the short circuit current density (jSC) are substantially lower. Overall it is demonstrated that AgNWs and the low temperature solution process of the buffer layer are an attractive device concept towards an indium free organic solar cell. Keywords http://www.sciencedirect.com/science/article/pii/S092702481200342X Metal nanowires; Transparent electrode; Solution processed; Aluminum-doped zinc oxide; Zinc oxide; Organic solar cells
11/05/14 10:50 SKP5050 Individually Position-Addressable Metal-Nanofiber Electrodes for Large-Area Electronics Yeongjun Le e, Tae-Sik Kim, Sung-Yong Min, Wentao Xu, Su-Hun Jeong, Hong-Kyu Seo andTae-Woo Lee Advanced Materials, 2014 Oct-14 A individually position-addressable large-scale-aligned Cu nanofiber (NF) array is fabricated using electro-hydrodynamic nanowire printing. The printed single-stranded Cu NF has diameter of about 710 nm and resistivity of 14.1 ë¼ë© cm and effectively used as source/drain nanoelectrodes in pentacene transistors, which show 25-fold higher hole mobility than that of a device with Cu thin-film electrodes. http://onlinelibrary.wiley.com/doi/10.1002/adma.201403559/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false metal nanofibers;Cu electrodes;electrode printing;nanofiber transistors;nanofiber electrodes
1/13/2014 14:53:03 UHV MechanoChemical synthesis of nanostructured Sr(Ti1‰ÛÒxFex)O3‰ÛÒë« solid-solution powders and their surface photovoltage responses Xiaofeng Chen, Qiong Luo, Mandi Han, Ooi Kiang Tan, Man Siu Tse, Hui Huang Journal of Solid State Chemistry, Volume 189, May 2012, Pages 80‰ÛÒ84 2012 A series of nanostructure Sr(Ti1‰öÕxFex)O3‰öÕë« (STFx, x=0.4, 0.6, 0.8) solid-solution powders were synthesized by mechanochemical approach milling from the mixture of SrO, Fe2O3 and TiO2 metal oxides at room temperature. The XRD results revealed that the perovskite STFx nanoparticles were finally formed with few residual ë±-Fe2O3 detected dependent on the milling conditions. The structure evolution suggested that the mechanochemical synthesis underwent via a solid-state reaction route to initially form Ti-rich perovskite and then incorporate with the residual ë±-Fe2O3 to achieve the estimated composition. The synthesized STF08 powders exhibited the significant Surface Photovoltage (SPV) spectrum response both in UV and in visible-light region with p-type semiconductor behavior. This finding suggested that the synthesized STF nanopowders could potentially utilize more solar spectrum energy effectively for photo-oxidation and photo-catalysis applications. http://www.sciencedirect.com/science/article/pii/S0022459612000266 Mechanochemical synthesis, Highenergy ball milling, Perovskite oxide, Surface photovoltage, Sr(Ti,Fe)O3‰öÕë«
06/02/15 14:39 SKP5050 Locally Welded Silver Nano-Network Transparent Electrodes with High Operational Stability by a Simple Alcohol-Based Chemical Approach Haifei Lu, Di Zhang, Jiaqi Cheng, Jian Liu, Jian Mao and Wallace C. H. Choy Advanced functional Materials, 2015 2015 As an indispensable aspect of emerging flexible optoelectronics, flexible transparent electrodes, especially those comprised of metal nanowires, have attracted great attentions recently. Welding the nanowire junctions is an effective strategy for reducing the sheet resistance and improving the operational stability of flexible nanowire electrode in practical applications. Herein, a simple alcohol-based solution approach is proposed to weld crossed silver nanowires by chemically growing silver ‰ÛÏsolder‰Û at the junctions of the nanowires, forming transparent silver nano-network electrodes with improved electrical conductivity and operational stability. Remarkably, silver nano-networks can be rapidly formed by this simple approach under ambient condition and room temperature, requiring no assistance from heat, light, electrical current, or mechanical pressure. Furthermore, our results show that the nano-network electrode formed from large diameter nanowires offers a better operational stability, whose trend is opposite to that of the untreated electrodes. To demonstrate the potential application of the highly stable silver nano-network from large diameter nanowires, organic solar cells fabricated on the nano-network electrode incorporated with silicon dioxide nanoparticles achieve comparable performance to the ITO control device. Consequently, strategy demonstrated in this work can contribute to low-cost and highly stable transparent electrodes in emerging flexible optoelectronics. http://onlinelibrary.wiley.com/doi/10.1002/adfm.201501004/abstract;jsessionid=70D24D1D2E6E75D78371F8AB16AE13DA.f02t03?deniedAccessCustomisedMessa ge=&userIsAuthenticated=false locally chemical welding; organic solar cells; silver nano-networks; nanoparticles; transparent electrodes
11/05/14 11:05 SKP5050 Over 1.1 eV Workfunction Tuning of Cesium Intercalated Metal Oxides for Functioning as Both Electron and Hole Transport Layers in Organic Optoelectronic Devices Xinchen Li, Fengxian Xie, Shaoqing Zhang, Jianhui Hou and Wallace C. H. Choy Advanced functional Materials, 2014 Sep-14 In this paper, over 1.1 eV continuous tuning of metal oxides workfunction is realized by cesium intercalation, making the metal oxide function as both electron transport layer and hole transport layer in organic optoelectronic devices. The demonstrated metal oxides are commonly used molybdenum oxide and vanadium oxide. The proposed approach of synthesizing cesium intercalated metal oxides has interesting properties of room-temperature, ambient atmosphere, water free and solution process, favoring the formation of metal oxides as carrier transport layers at different regions in multilayered devices and large scale fabrication of organic optoelectronics at low cost. Besides the wide range of controllable workfunction adjustment, band structures, and electrical properties are investigated in detail, to understand the effects of cesium intercalation on metal oxides. The device results show that, using the proposed cesium intercalation approach, each of the two investigated metal oxides can function as both ETL and HTL in organic solar cells and organic light emitting diodes with very good device performances. Consequently, with the interesting properties in film synthesis, the proposed cesium intercalated metal oxides can achieve continuously workfunction tuning over a large range and contribute to evolution of the simple route for fabricating high performance organic optoelectronic devices. http://onlinelibrary.wiley.com/doi/10.1002/adfm.201401969/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false large workfunction tuning;cesium intercalation;metal oxides carrier transport layers;room-temperature solution process;organic optoelectronic devices
10/29/2014 9:37:24 SKP5050 Passivation of n-type silicon (111) surfaces by the attachment of charged molecules. Alderman, N., Danos, L., Grossel, M. and Markvart, T. Photovoltaic Specialists Conference (PVSC), 2012, 38th IEEE Jun-12 With the drive for ever more efficient photovoltaics, the passivating layer becomes of greater importance. Currently, two main passivating mechanisms have been widely investigated; removal of surface states by organic layers and charging of surfaces to invert the surface bands. Our paper aims to increase the knowledge of this area by combining the removal of surface states with charging, in an attempt to build ever more efficient passivation layers. It was found that upon immersion in base, the recombination lifetime significantly improved from around 8 ë¼s to over 30 ë¼s, due to a negative monolayer surface charge. As the charge is further from the silicon surface, both the recombination lifetime and surface photovoltage (SPV) decrease. This in turn indicates a reduction in the surface electron concentration. Once the surface charge is neutralized, both the recombination lifetime and SPV return to their starting value. http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6317769&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6317769 Kelvin, passivation, radiative recombination, silicon, surface charge, charge carrier lifetime, surface photovoltage, solar cells
02/06/14 17:23 SKP5050 with SPV Characterization of optoelectronic properties of the ZnO nanorod array using surface photovoltage technique Yiting Liu, Ai min LiuCorresponding author contact information, E-mail the corresponding author, Weifeng Liu, Zengquan Hu, Yongchang Sang Applied Surface Science Volume 257, Issue 4, 1 December 2010, Pages 1263‰ÛÒ1266 2010 Well-aligned ZnO nanorod array, synthesized by wet chemical bath deposition (CBD) method on conductive indium‰ÛÒin-oxide (ITO) substrate, was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. Surface photovoltage (SPV) technique based on a scanning Kelvin Probe system was employed to investigate the optoelectronic behavior of ZnO nanorod array. The surface photovoltage and its time-resolved evolution process are used to determine the energy level structure of the ZnO nanorod array. http://www.sciencedirect.com/science/article/pii/S0169433210011177 Kelvin Probe; Surface photovoltage; ZnO; Nanorod array
1/13/2014 14:25:28 SKP 5050 Effect of Zr doping power on the electrical, optical and structural properties of In‰ÛÒZr‰ÛÒO anodes for P3HT: PCBM thin-film organic solar cells Da-Young Ch o, Kwun-Bum Chung, Seok-In Na and Han-Ki Kim J. Phys. D: Appl. Phys. 46 (2013) 295305 2013 We investigated the effect of Zr doping power on the electrical, optical, structural and morphological properties of ZrO2 and In2O3 co-sputtered In‰ÛÒZr‰ÛÒO (IZrO) thin films as transparent anodes for bulk-heterojunction organic solar cells (OSCs). Increased Zr doping power led to increased resistivity of as-deposited IZrO films while decreased resistivity of IZrO films annealed at 500 å¡C. Regardless of the Zr doping power, the IZrO film showed a high optical transmittance in the visible wavelength region and near infrared (NIR) wavelength region. The optimized IZrO film doped with 50 W ZrO2 radio frequency power showed a sheet resistance of 20.71 ë©/square and transmittance of 83.9%, which is comparable to the value of conventional In‰ÛÒSn‰ÛÒO (ITO) films. The electronic structures measured by spectroscopic ellipsometry indicated expansion of unoccupied states near the conduction band with increased ZrO2 doping power. OSCs with transparent IZrO anodes exhibited similar performances to OSCs with reference ITO anodes due to the similar optical properties of IZrO and ITO films in the visible wavelength region. Due to their high transmittance in the NIR wavelength region, IZrO films are a promising replacement for ITO anodes in NIR absorbing OSCs. http://iopscience.iop.org/0022-3727/46/29/295305 IZrO, thin films, organic solar cells
11/05/14 11:51 KP020 Efficiency boosting of inverted polymer solar cells with a polyvinylpyrrolidone-modified Al-doped ZnO electron transport layer Xuan Yu, Xiaoming Yu, Jianjun Zhang, Gengshen Zhao, Jian Ni, Hongkun Cai and Ying Zhao Solar Energy Materials and Solar Cells (128), 2014, pp. 307-312. Sep-14 A polyvinylpyrrolidone (PVP) thin film (9 nm) prepared on the top of Al-doped ZnO (AZO) electron transport layer by spin-coating, was developed as an interface modifier in inverted polymer solar cells (IPSCs). The PVP with excellent alcohol solubility provided a strong adhesion and wettability, leading to an improved interface quality between the AZO and active layer. Combined with a reduced work function of the AZO layer, the resulting devices showed a significant increase in power conversion efficiency from 2.86% to 4.08%, benefiting from the dramatic enhancement in fill factor (35%). Due to the ease of use and remarkable boost in efficiency, our results indicated that PVP was a promising candidate for surface modification material in IPSCs. http://www.sciencedirect.com/science/article/pii/S0927024814002335 Inverted polymer solar cells; PVP; Surface modification; Al-doped ZnO
02/03/15 14:42 KP020 Efficient inverted polymer solar cells based on surface modified FTO transparent electrodes Xiaoming Yu, Xuan Yu, Jianjun Zhang, Dekun Zhang, Jian Ni, Hongkun Cai, Dexian Zhang, Ying Zhao Solar Energy Materials and Solar Cells (136), 2015, pp. 142 - 147. May-15 Nano-textured transparent electrodes are commonly used to receive higher light absorption in inverted polymer solar cells (IPSC). However, the performance of the device is often restricted by the highly rough morphology of the textured transparent electrode. In this work, a Polyvinylpyrrolidone (PVP) interlayer was inserted as a surface modifier in IPSCs based on a fluorine-doped SnO2 electrode (FTO). The inserted layer facilitates electron extraction due to improved interface morphology of the AZO electron transport layer (ETL). This enhancement resulted in an approximately 63% increase in power conversion efficiency from 2.52% to 4.14% of IPSCs based on the FTO electrode compared to solar cells without PVP layer. http://www.sciencedirect.com/science/article/pii/S0927024815000057 Inverted polymer solar cells; FTO; PVP surface modification; Al-doped ZnO
6/16/2015 11:33:28 * Improvement in polymer solar cell performance and eliminating light soaking effect via UV-light treatment on conjugated polyelectrolyte interlayer Xianqiang Li, Jie Liu, Xiaohong Tang, Shifeng Guo, Jun Li, Hong Wang, Bin Liu, Wei Lin Leong Organic Electronics, 2015 2015 A new conjugated polyelectrolyte material, namely, poly [9,9-bis((6‰Û²-N,N,N-trimethylamino)hexyl)-fluorene-alt-co-benzoxadiazole dibromide] (PFBD) is reported as electron transport layer (ETL) in polymer solar cells. We observed a light-soaking effect and described how a pre UV-light treatment on PFBD ETL is essential for attaining higher efficiencies (>7%) and negate the light-soaking problem. The pre UV-light treatment on PFBD layer is found to directly influence its molecular structure and result in reduction of the work function and increased electron mobility in PFBD which corroborates well with the observed low series resistances obtained from dark current analysis and impedance spectra, and therefore enhancement in open-circuit voltage and fill factor. Moreover, after the pre-UV light treatment, the maximal efficiency of the solar cells retains at a nearly similar level for at least 26 days. http://www.sciencedirect.com/science/article/pii/S1566119915002608 Inverted polymer solar cell; Conjugated polyelectrolyte; Light-soaking effect; Electron-transporting layer
1/13/2014 14:32:18 KP + SPV Spectroscopic Evidence of Work Function Alterations Due to Photoswitchable Monolayers on Gold Surfaces Matthew A. Bartucci, Jan FloriÌÁn, and Jacob W. Ciszek J. Phys. Chem. C, 2013, 117 (38), pp 19471‰ÛÒ19476 2013 Taking advantage of surfaces‰Ûª response to interfacial dipoles, a class of photochromophores (dihydroindolizine) is demonstrated to alter the work function of the underlying substrate ( 170 meV). This same molecule also provides spectroscopic signatures for correlating the change in molecular structure to the induced change in the surfaces‰Ûª electronic properties. Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) allows analysis of the characteristic dihydroindolizine C‰¥C (1559 cm‰ÛÒ1) and pyridinium (1643 cm‰ÛÒ1) stretch as a function of photoexcitation. Structural assignments of this photochromophore are corroborated to density function theory calculations. Conformational changes in the monolayers appear in parallel with work function changes and are consistent with both its rate and magnitude. http://pubs.acs.org/doi/abs/10.1021/jp405710u interfacial dipoles, photochromophores, gold
11/05/14 09:19 SKP5050 Improving the Organic Semiconductor- Metal Contact Interface in Printed High Performance Organic TFTs Kanan Puntambekar, Lisa Stecker, Kurt Ulmer, Themistokles Afentakis and Steven Droes MRS Procee dings (1402), 2012 Feb-12 Optimization of the interface between the organic semiconductor (OSC) & the source-drain (S/D) electrode is critical in order to improve organic thin film transistor (OTFT) device performance. This process typically involves coating the metal S/D electrodes with an optimal self-assembled thiol layer; a process that requires pristine metal surfaces for successful treatment. Obtaining contamination free surfaces can be challenging in the case of printed metal electrodes. Here we demonstrate an effective strategy to address this issue by introducing a brief low power forming gas plasma treatment prior to the surface coating step. We show a two orders of magnitude decrease in the contact resistance as a result of this treatment. http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8486692&fileId=S1946427412001893 ink-jet printing; devices; organic
1/13/2014 14:57:49 KP The electronic transport mechanism in indium molybdenum oxide thin films RF sputtered at room temperature Elangovan El amurugu, Parthiban Shanmugam, Goncalo Goncalves, Nuno Franco, Eduardo Alves, Rodrigo Martins and Elvira Fortunato Europhysics Letters, Volume 97, Number 3 (2012) 2012 Indium molybdenum oxide (IMO) thin films were radio-frequency (RF) sputtered at room temperature (RT) and studied as a function of base pressure (BP). The crystallinity of the films is decreased with the increase in BP. A maximum mobility (ë¼) of 49.6‰Ûäcm2‰ÛäV‰öÕ1‰Ûäs‰öÕ1 was obtained from the IMO films deposited at RT without any post-annealing treatment. The electronic behaviour of the deposited films was investigated by temperature-dependent (100‰ÛÒ550‰ÛäK) Hall measurements. Study on the scattering mechanisms based on the experimental data and theoretical models show that the ionized scattering centres are dominating. The films possess wide work function (4.91‰ÛäeV) and high transmittance (> 70%) over visible and near infrared (NIR) range. The obtained results, especially the high work function and NIR transmittance, are very promising particularly in applications such as optical detectors and solar cells. http://iopscience.iop.org/0295-5075/97/3/36002 IMO, thin films, crystallinity, work function, transmittance, optical detectors, solar cells
1/13/2014 14:15:55 SKP 5050 Near infra-red transparent Mo-doped In2O3 by hetero targets sputtering for phosphorescent organic light emitting diodes Yong-Hee Shin, Sin-Bi Kang, Sunghun Lee, Jang-Joo Kim, Han-Ki Kim Organic Electronics 14 (2013) 926‰ÛÒ933 2013 We report a highly near infrared (NIR) transparent MoO3-doped In2O3 (IMO) film prepared by hetero target sputtering for use as a transparent anode in phosphorescent organic light emitting diodes (OLEDs). Effective activation of Mo dopant in the In2O3 matrix and good crystallinity with the (2 2 2) preferred orientation from by rapid thermal annealing (RTA) led to the lowest resistivity of 4.25 Ì— 10‰öÕ4 Ohm cm and sheet resistance of 16.9 Ohm/square, comparable to a conventional ITO anode without lose of transparency in the NIR region. Due to high carrier mobility in the IMO matrix, IMO film exhibited higher transmittance in the visible and NIR regions compared to ITO film even though it has a similar resistivity. Both synchrotron X-ray scattering and high resolution transmission electron microscope examinations showed that the optimized IMO film annealed at 600 å¡C had a rectangular shaped columnar structure with a strongly preferred (2 2 2) orientation. Identical current density‰ÛÒvoltage‰ÛÒluminance and quantum efficiency of the phosphorescent OLED fabricated on an IMO anode were comparable to those of the OLED on a reference ITO anode due to the high transparency and low resistivity of the IMO anode. http://www.sciencedirect.com/science/article/pii/S1566119913000086 IMO, organic light emitting diodes
4/14/2015 11:18:02 SKP5050 Designing and synthesis of imidazole based hole transporting material for solid state dye sensitized solar cells Ramanpreet Kaur Aulakh, Sana Sandhu, Tanvi, Sandeep Kumar, Aman Mahajan, R.K. Bedi and Subodh Kumar Synthetic Metals 205, 2015, 92 - 97 2015 The present paper involves the development of novel imidazole based non-planar, small size, highly soluble and thermally stable hole transporting material (HTM) namely 2-(1-(anthracen-2-yl)-4,5-diphenyl-1H-imidazol-2-yl) phenol (TPAN) to improve the stability of dye sensitized solar cell (DSSC). The molecule has been investigated in solution and thin film form for their structural, photo physical and electrical properties by experimental as well as quantum chemical techniques. A solid state dye sensitized solar cell (SSDSSC) using this newly synthesised HTM has been fabricated and characterized for their photovoltaic performance under illumination. http://www.sciencedirect.com/science/article/pii/S0379677915001472 Imidazole; Hole transport material; Solid state dye sensitized solar cell
1/13/2014 14:27:45 SKP 5050 Probing gas response of pure and Au modified ZnO nanowires network using work function measurements Preetam K. Sharma, Niranjan S. Ramgir, N. Datta, M. Kaur, C. P. Goyal, S. Kailasaganapathi, A. K. Debnath, D. K. Aswal, and S. K. Gupta AIP Conf. Proc. 1512, pp. 346-347 (2013) 2013 Work function of the material is a strong indicator of the state of a surface and its surrounding. Au being an excellent promoter for H2S, work function changes of pure and Au modified ZnO network films upon exposure to gas have been investigated using Kelvin probe method. Au modified ZnO sample exhibited a work function of 5.42 eV which is ‰ö¼320 meV higher than that of pure ZnO sample (5.10 eV). This increase could be attributed to the nano-Schottky type of barrier junction formed between Au and ZnO nanowires. Exposure to H2S resulted in decrease of work function for both pure and Au modified ZnO NWs network films. H2S being reducing in nature, this decrease can be accounted on the basis of Fermi level shift due to large number of electrons that the gas donates to the matrix upon interaction with adsorbed oxygen species. http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.4791053 II-VI semiconductors, zinc oxide films, work functions, gold, nanowires, electron gas, Fermi levels, stress strain relations, surface states
11/04/14 21:46 SKP5050 Fabrication and characterization of tunable polysaccharide hydrogel blends for neural repair Jonathan M. Zuidema, Matthew M. Pap, David B. Jaroch, Faith A. Morrison and Ryan J. Gilbert Acta Biomaterialia (7:4), 2011 pp.1634-1643 Apr-11 Hydrogels are an important class of biomaterials that have the potential to be used as three-dimensional tissue engineering scaffolds for regenerative medicine. This is especially true in the central nervous system, where neurons do not have the ability to regenerate due to the prohibitory local environment following injury. Hydrogels can fill an injury site, replacing the growth-prohibiting environment with a more growth-permissive one. In this study, dextran and chitosan were incorporated into a methylcellulose and agarose hydrogel blend. This created several thermally sensitive polysaccharide hydrogel blends that had tunable mechanical and surface charge properties. Cortical neurons were cultured on the hydrogels to determine the blend that had the greatest neuron compatibility. Our results show that softer, more positively charged polysaccharide hydrogel blends allow for greater neuron attachment and neurite extension, showing their promise as CNS regeneration scaffolds. http://www.sciencedirect.com/science/article/pii/S1742706110005465 Hydrogel; Nerve; Chitosan; Mechanical properties; Thermally responsive material
1/13/2014 15:03:50 KP 020 Characterization of new transparent organic electrode materials Scott A. Mauger, Adam J. MoulÌ© Organic Electronics, Volume 12, Issue 11, November 2011, Pages 1948‰ÛÒ1956 2011 We characterize thin films of a new conductive copolymer, sulfonated poly(thiophene-3-[2-(2-methoxyethoxy)ethoxy]-2,5-diyl) (S-P3MEET), with various chemical additives to determine if the films are suitable for use as a hole transport layer in organic electronic devices. Using atomic force microscopy, Kelvin probe, and contact angle measurements, we probe the surface morphology and composition of S-P3MEET thin films. We then use DC conductivity measurements and spectroscopic ellipsometry to determine how the additives change the bulk properties of the films. We find that the additives decrease conductivity, increase work function, and alter the complex refractive index. The resulting properties make some preparations of S-P3MEET advantageous for use in light emitting diodes. http://www.sciencedirect.com/science/article/pii/S1566119911002849 hole transport layer, organic photovoltaics, organic light emitting diodes, PEDOT:PSS, S-P3MEET
10/29/2014 9:12:25 SKP5050 Growth and Electrical Transport Properties of Organic Semiconductor Thin Films Arvind Kuma r, R. Prasad, A. K. Debnath, Ajay Singh, S. Samanta, D. K. Aswal and S. K. Gupta Solid State Phenomena (209), 2013, pp. 1-5. Nov-13 Hexadecafluorophthalocyanine (F16CuPc) and Cobalt phthalocyanone (CoPc) thin films of different thickness (20-200nm) have been grown by Molecular Beam Epitaxy (MBE) using different deposition rate (0.2 ‰ÛÒ 1.0 ÌÉ/s). For nanowire type growth lower deposition rate and for films of smooth surface higher deposition rate are found suitable. Charge transport (J~V) of CoPc and F16CuPc films is governed by bulk-limited processes with a bias dependent crossover from Ohmic to trap-free space-charge-limited conduction. The mobility (ë¼) values at 300 K were found 4.5 and 5.5 cm2 V‰öÕ1 s‰öÕ1 for CoPc and F16CuPc films respectively. Mechanism of reverse rectification behavior of an organic heterojunction comprising of CoPc and F16CuPc is explained by Kelvin Probe measurement. http://www.scientific.net/SSP.209.1 Hexadecafluorophthalocyanine, mobility, molecular beam epitaxy, space charge limited conduction
1/13/2014 14:37:04 SKP 5050 Electron accumulation/depletion at F16CoPc/Znq3 heterojunction: Kelvin probe and charge transport study Ashwini Kumar, R. Prasad, Arvind Kumar, Soumen Samanta, Ajay Singh, A. K. Debnath, D. K. Aswal, and S. K. Gupta AIP Conf. Proc. 1512, pp. 770-771 (2013) 2013 We have synthesized n-n isotype organic heterojunction comprising of n-type cobalt hexadecafluorophthalocyanine ( F16CoPc )/n-type tris(8-hydroxyquinoline)zinc ( Znq3 ) thermal evaporation method. Using Kelvin probe we found that electrons are accumulated atF16CoPc and depleted in Znq3 sides of interface. The total thickness of electrons accumulation and depletion were found to be 16 nm. Electron accumulation was further confirmed by charge transport measurement. http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.4791265 heterojunctions, cobalt, electric measurements
11/04/14 21:32 SKP5050 Determination of Schottky barrier heights and Fermi-level unpinning at the graphene/n-type Si interfaces by x-ray photoelectron spectroscopy and Kelvin probe Yow-Jon Lin and Jian-Jhou Zeng Applied Surface Science, 2014 2014 The interface characteristics of graphene/n-type Si samples using x-ray photoelectron spectroscopy (XPS) measurements are investigated. XPS makes it possible to extract a reliable Schottky barrier value. For graphene/n-type Si samples with (without) sulfide treatment, the Schottky barrier height is 0.86 (0.78) eV. The Schottky barrier height was increased from 0.78 to 0.86 eV, indicating that sulfide treatment is effective in passivating the surface of n-Si (owing to the formation of Si-S bonds). To determine the Fermi-level pinning/unpinning at the graphene/n-type Si interfaces with sulfide treatment, an analysis is conducted according to the Schottky-Mott limit and the actual work function of graphene is examined with the Kelvin probe. It is shown that the Fermi energy level is unpinned and the Schottky barrier value is dependent on the work function of graphene. Investigation of graphene/n-type Si interfaces is important, and providing the other technique for surface potential control is possible. http://www.sciencedirect.com/science/article/pii/S0169433214023010 Graphene; Si; Schottky barrier height; Work function
11/05/14 10:36 SKP5050 Organic Solar Cells with Graphene Electrodes and Vapor Printed Poly(3,4-ethylenedioxythiophene) as the Hole Transporting Layers Hyesung Park, Rachel M. Howden, Miles C. Barr, Vladimir Bulovi€à, Karen Gleason and Jing Kong ACS Nano (6: 7), 2012, pp. 6370-6377 Jun-12 For the successful integration of graphene as a transparent conducting electrode in organic solar cells, proper energy level alignment at the interface between the graphene and the adjacent organic layer is critical. The role of a hole transporting layer (HTL) thus becomes more significant due to the generally lower work function of graphene compared to ITO. A commonly used HTL material with ITO anodes is poly(3,4-ethylenedioxythiophene) (PEDOT) with poly(styrenesulfonate) (PSS) as the solid-state dopant. However, graphene‰Ûªs hydrophobic surface renders uniform coverage of PEDOT:PSS (aqueous solution) by spin-casting very challenging. Here, we introduce a novel, yet simple, vapor printing method for creating patterned HTL PEDOT layers directly onto the graphene surface. Vapor printing represents the implementation of shadow masking in combination with oxidative chemical vapor deposition (oCVD). The oCVD method was developed for the formation of blanket (i.e., unpatterened) layers of pure PEDOT (i.e., no PSS) with systematically variable work function. In the unmasked regions, vapor printing produces complete, uniform, smooth layers of pure PEDOT over graphene. Graphene electrodes were synthesized under low-pressure chemical vapor deposition (LPCVD) using a copper catalyst. The use of another electron donor material, tetraphenyldibenzoperiflanthene, instead of copper phthalocyanine in the organic solar cells also improves the power conversion efficiency. With the vapor printed HTL, the devices using graphene electrodes yield comparable performances to the ITO reference devices (ëáp,LPCVD = 3.01%, and ëáp,ITO = 3.20%). http://pubs.acs.org/doi/abs/10.1021/nn301901v graphene; APCVD; LPCVD; organic solar cell; oCVD PEDOT; vapor printing; poly(3,4-ethylenedioxythiophene); chemical vapor deposition
1/13/2014 14:14:20 SKP5050 Tuning the work function of graphene by ultraviolet irradiation Yow-Jon Lin and Jian-Jhou Zeng Appl. Phys. Lett. 102, 183120 (2013) 2013 Graphene layers grown by chemical vapor deposition were, respectively, irradiated for 0, 20, 40, and 60‰Ûämin by an ultraviolet light source in order to experimentally study the change in the work function of graphene. The dependences of the work function and carrier concentration upon ultraviolet irradiation have been found. It is shown that ultraviolet irradiation may lead to oxygen desorption, thus reducing the hole density and work function of graphene. Based on the well-known expression for the Fermi energy of Dirac fermions, the Fermi velocity of graphene was extracted to be about 5.2‰ÛäÌ—‰Ûä105‰Ûäm/s. http://scitation.aip.org/content/aip/journal/apl/102/18/10.1063/1.4804289 graphene, work functions, ultraviolet light, ultraviolet radiation effects, gold, carrier density, adsorbates, copper, Dirac equation, semiconductor growth
10/02/14 10:37 SKP5050 Tuning the work function of graphene by nitrogen plasma treatment with different radio-frequency powers Jian-Jhou Ze ng, Yow-Jon Lin Applied Physics Letters Jun-14 Graphene prepared by the chemical vapor deposition method was treated with nitrogen plasma under different radio-frequency (rf) power conditions in order to experimentally study the change in the work function. Control of the rf power could change the work function of graphene from 4.91 eV to 4.37 eV. It is shown that the increased rf power may lead to the increased number of graphitic nitrogen, increasing the electron concentration, and shifting the Fermi level to higher energy. The ability to controllably tune the work function of graphene is essential for optimizing the efficiency of optoelectronic and electronic devices. http://dx.doi.org/10.1063/1.4882159 Graphene, Work Function, Radio-Frequency, Nitrogen Plasma Treatment
10/06/14 13:07 SKP5050 Tuning electrical parameters of graphene/p-type polycrystalline silicon Schottky diodes by ultraviolet irradiation Jian-Huang Lin, Yow-Jon Lin, Hsing-Cheng Chang Applied Physics A: Materials Science & Processing Jul-14 The present work reports the fabrication and detailed electrical properties of graphene/p-type polycrystalline silicon (poly-Si) Schottky diodes with and without ultraviolet irradiation. Ultraviolet treatment may lead to the reduced work function of graphene, thus increasing the Schottky barrier height at the graphene/poly-Si interface. Compared to the graphene/poly-Si Schottky diodes without ultraviolet treatment, the ultraviolet-treated graphene/poly- Si Schottky diodes exhibit lower ideality factor and higher responsivity. The sensitivity of the work function of graphene to the ultraviolet irradiation time provides an opportunity to tune the electrical parameters of graphene/ poly-Si Schottky diodes. The ability to controllably tune the work function of graphene is essential for optimizing the efficiency of optoelectronic and electronic devices. http://link.springer.com/article/10.1007%2Fs00339-014-8742-3 Graphene, Silicon, Work Function, Schottky Diodes, UV treatment
11/04/14 14:46 SKP5050 Electronic transport for graphene/n-type Si Schottky diodes with and without H2O2 treatment Jian-Huang Lin, Jian-Jhou Zeng and Yow-Jon Lin Thin Solid Films (550:1), 2014, pp. 582-586. Jan-14 Developing better contacts on Si is one of the main challenges for Si-based device technology. The present work reports the fabrication and detailed electrical properties of graphene/n-type Si Schottky diodes. The graphene/n-type Si Schottky diode without H2O2 treatment shows a poor rectifying behavior with an ideality factor (ëá) of 3.5 and high leakage. ëá > 2 implies that the interfacial defects influence the electronic conduction through the device. However, the graphene/n-type Si Schottky diode with H2O2 treatment shows a good rectifying behavior with ëá of 1.9 and low leakage. Such an improvement indicates that a good passivation is formed at the interface as a result of the reduction of the defect density. These experimental demonstrations suggest that it may be possible to minimize the adverse effects of the interface states to obtain functional devices using H2O2 treatment. http://www.sciencedirect.com/science/article/pii/S0040609013019354 Graphene, Si, diode, electrical property, defect
1/13/2014 14:49:06 KP 020 The influence of substrate morphology on thickness uniformity and unintentional doping of epitaxial graphene on SiC Jens Eriksson, Ruth Pearce, Tihomir Iakimov, Chariya Virojanadara, Daniela Gogova, Mike Andersson, Mikael Syvajarvi, Anita Lloyd Spetz, and Rositza Yakimova Applied Physics Letters 100, 241607 (2012) 2012 A Pivotal issue for the fabrication of electronic devices on epitaxialgraphene on SiC is controlling the number of layers and reducing localized thickness inhomogeneities. Of equal importance is to understand what governs the unintentional doping of the graphene from the substrate. The influence of substrate surface topography on these two issues was studied by work function measurements and local surface potential mapping. The carrier concentration and the uniformity of epitaxialgraphene samples grown under identical conditions and on substrates of nominally identical orientation were both found to depend strongly on the terrace width of the SiC substrate after growth. http://scitation.aip.org/content/aip/journal/apl/100/24/10.1063/1.4729556 graphene, doping, epitaxy, work functions, carrier density, surface charge, surface morphology, silicon, carbides, charge transfer
11/04/14 21:49 SKP5050 Highly near-infrared transparent GeO2-doped In2O3 electrodes for bulk heterojunction organic solar cells Sin-Bi Kang, J ong-Wook Lim, Seok-In Na and Han-Ki Kim Solar Energy Materials and Solar Cells (107), 2012, pp.373-380 Dec-12 We report on the characteristics of GeO2-doped In2O3 (IGO) films for use as transparent electrodes in organic solar cells (OSCs). The electrical, optical, and structural properties of IGO electrodes were investigated as a function of RF power and post-annealing conditions. At optimized conditions, the IGO electrode exhibited a low sheet resistance of 14.0 ë©/square, a high optical transmittance of 86.9%, a root mean square roughness of 1.27 nm and a work function of 5.2 eV. In particular, the IGO film showed higher optical transmittance in the near-infrared region due to a lower free carrier concentration and higher mobility than conventional ITO electrodes. The higher Lewis acid strength of the Ge4+ (3.06) dopant, compared to that of a Sn4+ (1.62) dopant, led to higher mobility of the IGO films. In addition, we observed that the strongly oriented (222) grains in the IGO films enhanced carrier mobility and relaxation time. Furthermore, a bulk heterojunction OSC with the optimized IGO anode exhibited a good cell performance with a fill factor of 67.38%, a short circuit current of 8.438 mA/cm2, an open circuit voltage of 0.606 V, and a power conversion efficiency of 3.443%, which are comparable to OSCs with ITO anodes. http://www.sciencedirect.com/science/article/pii/S0927024812003790 GeO2-doped In2O3; Transparent electrodes; Organic solar cells; Lewis acid strength
02/03/15 14:07 SKP5050 A Universal Interface Layer Based on an Amine-Functionalized Fullerene Derivative with Dual Functionality for Efficient Solution Processed Organic and Perovskite Solar Cells Hamed Azimi, Tayebeh Ameri, Hong Zhang, Yi Hou, Cesar Omar Ramirez Quiroz, Jie Min, Mengyao Hu, Zhi-Guo Zhang, Thomas Przybilla, Gebhard J. Matt, Erdmann Spiecker, Yongfang Li and Christoph J. Brabec Advanced Energy Materials, 2015 Jan-15 The successful application of an effective dipolar interface layer based on an amine functionalized fullerene derivative (DMAPA-C60) is reported for the perovskite and organic photovoltaic devices. The incorporation of DMAPA-C60 facilities a favorable energy level alignment, and results in enhanced mobility-lifetime (åµt) product. http://onlinelibrary.wiley.com/doi/10.1002/aenm.201401692/abstract;jsessionid=C98928537E1E2152C2630F440DA1AC94.f02t01?deniedAccessCustomisedMessa ge=&userIsAuthenticated=false energy level alignment; mobility-lifetime products; organic photovoltaic devices; perovskite solar cells
1/13/2014 14:59:32 SKP 5050 Advancing MIM Electronics: Amorphous Metal Electrodes E. William C owell III, Nasir Alimardani, Christopher C. Knutson, John F. Conley Jr., Douglas A. Keszler, Brady J. Gibbons, John F. Wager Advanced Materials, Volume 23, Issue 1, pages 74‰ÛÒ78, January 4, 2011 2011 Amorphous metal thin films with atomically smooth surfaces are employed as contact layers for the realization of metal-insulator-metal (MIM) devices operating on the basis of controlled quantum mechanical tunneling through an ultrathin dielectric. http://onlinelibrary.wiley.com/doi/10.1002/adma.201002678/full electronic structures, charge transport, thin films, electrodes, metals
06/02/15 14:44 * The relationship between the electron work function and friction behavior of passive alloys under different conditions Shiyi Liu, Ha o Lu and D.Y. Li Applied Surface Science, 2015 2015 Electron work function (EWF), adhesion and friction coefficient of three passive alloys were investigated. During dry sliding tests, surfaces having higher work functions showed larger coefficients of friction. While under oil-lubricated sliding condition, the trend was reversed. It appears that when the surface passive film was damaged, the surface broken atomic bonds became active, leading to larger friction. However, under the oil-lubricated sliding condition, the passive film was retained, resulting in a different trend. Surface adhesive forces of freshly polished surfaces and etched ones were measured using an atomic force microscope. Results of the adhesion measurement are consistent with the behaviors of the alloys observed during the friction tests. http://www.sciencedirect.com/science/article/pii/S0169433215012532 Electron work function; Friction; Adhesion; Alloys
1/13/2014 14:37:44 SKP 5050 Application of in situ measurement of photo-induced variations in electron work functions for in-depth understanding of the photocatalytic activity of TiO2 nanotubes Ning Fu, Xin hu Tang and Dongyang Li         Nanotechnology 23 (2012) 275704 2012 The electron work function (EWF) is the minimum energy required to move an electron at the Fermi level from inside a conducting material to its surface with zero kinetic energy. This fundamental parameter is directly related to many chemical, physical, and mechanical properties of materials. In this work, variations in EWF of TiO2 nanotube arrays under light illumination were monitored in situ using a Kelvin probe in order to study the photon-induced electron excitation in the TiO2nanotubular arrays upon illumination. It was shown that the EWF could be used to investigate the electron‰ÛÒhole separation and recombination, helping us to better understand the photo-activity of the photocatalytic material. This study has demonstrated that EWF provides an effective parameter for understanding of semiconductors' photo-activities with different views that may not be achieved using traditional techniques, such as diffuse reflection spectroscopy and photoelectrochemical measurement. http://iopscience.iop.org/0957-4484/23/27/275704 electron work function, TiO2 nanotube arrays, electron‰ÛÒhole recombination, photocatalytic material
1/13/2014 14:29:22 KP 020 Transparent organic thin film transistors with WO3/Ag/WO3 source-drain electrodes fabricated by thermal evaporation Nan Zhang, Y ongsheng Hu, and Xingyuan Liu Appl. Phys. Lett. 103, 033301 (2013) 2013 High-performance transparent organic thin film transistors using a WO3/Ag/WO3 (WAW) multilayer as the source and drain electrodes have been developed without breaking the vacuum. The WAW electrodes were deposited by thermal evaporation at room temperature, leading to little damage to organic film. The optimized WAW electrode shows high transmittance (86.57%), low sheet resistance (11 ë©/sq), and a high work function (5.0‰ÛäeV). Consequently, we obtained high performance devices with mobility of 8.44‰ÛäÌ—‰Ûä10‰öÕ2 cm2/V‰Ûäåá‰Ûäs, an on/off ratio of approximately 1.2‰ÛäÌ—‰Ûä106, and an average visible range transmittance of 81.5%. http://scitation.aip.org/content/aip/journal/apl/103/3/10.1063/1.4813838 electrodes, silver, contact resistance, electrodeposition, sputter deposition, work functions, thin films, thin film devices, vacuum deposition, thin film transistors
1/13/2014 15:05:19 SPV Electro-optic investigation of the surface trapping efficiency in n-alkanethiol SAM passivated GaAs(001) Gregory M Marshall, Gregory P Lopinski, Farid Bensebaa and Jan J Dubowski Nanotechnology 22 (2011) 235704 2011 The electro-optic characteristics of the semi-insulating and n + -type GaAs(001) surfaces passivated with n-alkanethiol self-assembled monolayers were investigated using Kelvin probe surface photovoltage (SPV) and photoluminescence (PL) techniques. Referencing the equilibrium surface barrier height established in an earlier report, SPV measurements demonstrated a significant (>100 mV) increase in the non-equilibrium band-bending potential observed under low-level photo-injection. Modeling of the SPV accounts for these observations in terms of a large (>104) decrease in the hole/electron ratio of surface carrier capture cross-sections, which is suggested to result from the electrostatic potential of the interfacial dipole layer formed upon thiol chemisorption. The cross-section effects are verified in the high-injection regime based on carrier transport modeling of the PL enhancement manifested as a reduction of the surface recombination velocity. http://iopscience.iop.org/0957-4484/22/23/235704 electro-optic characteristics, surface photovoltage, equilibrium surface barrier height, non-equilibrium band-bending potential, surface carrier capture, surface recombination velocity
1/13/2014 15:00:10 SKP 5050 Electrical Potential of Acupuncture Points: Use of a Noncontact Scanning Kelvin Probe Brian J. Gow, Justine L. Ch eng, Iain D. Baikie, Ì÷rjan G.Martinsen, Min Zhao, Stephanie Smith, and Andrew C. Ahn * 2011 Evidence-Based Complementary and Alternative Medicine, Volume 2012, Article ID 632838 Objective. Acupuncture points are reportedly distinguishable by their electrical properties. However, confounders arising from skin-to-electrode contact used in traditional electrodermal methods have contributed to controversies over this claim. The Scanning Kelvin Probe is a state-of-the-art device that measures electrical potential without actually touching the skin and is thus capable of overcoming these confounding effects. In this study, we evaluated the electrical potential profiles of acupoints LI-4 and PC-6 and their adjacent controls. We hypothesize that acupuncture point sites are associated with increased variability in potential compared to adjacent control sites. Methods. Twelve healthy individuals were recruited for this study. Acupuncture points LI-4 and PC-6 and their adjacent controls were assessed. A 2‰Ûämm probe tip was placed over the predetermined skin site and adjusted to a tip-to-sample distance of 1.0‰Ûämm under tip oscillation settings of 62.4‰ÛäHz frequency. A 6 Ì— 6 surface potential scan spanning a 1.0‰Ûäcm‰ÛäÌ—‰Ûä1.0‰Ûäcm area was obtained. Results. At both the PC-6 and LI-4 sites, no significant differences in mean potential were observed compared to their respective controls (Wilcoxon rank-sum test, P = 0.73 and 0.79, resp.). However, the LI-4 site was associated with significant increase in variability compared to its control as denoted by standard deviation and range (P = 0.002 and 0.0005, resp.). At the PC-6 site, no statistical differences in variability were observed. Conclusion. Acupuncture points may be associated with increased variability in electrical potential. http://www.ncbi.nlm.nih.gov/pubmed/23320033 electrical potential, biological tissues
6/30/2015 10:25:25 SKP5050 A New Inter onnecting Layer of Metal Oxide/Dipole Layer/Metal Oxide for Efficient Tandem Organic Solar Cells Shunmian Lu, Xing Guan, Xinchen Li, Wei E. I. Sha, Fengxian Xie, Hongchao Liu, Jiannong Wang, Fei Huang and Wallace C. H. Choy Advanced Energy Materials, 2015 2015 A new metal-oxide-based interconnecting layer (ICL) structure of all-solution processed metal oxide/dipole layer/metal oxide for efficient tandem organic solar cell (OSC) is demonstrated. The dipole layer modifies the work function (WF) of molybdenum oxide (MoO x ) to eliminate preexisted counter diode between MoO x and TiO2. Three different amino functionalized water/alcohol soluble conjugated polymers (WSCPs) are studied to show that the WF tuning of MoO x is controllable. Importantly, the results show that S-shape current density versus voltage (J‰ÛÒV) characteristics form when operation temperature decreases. This implies that thermionic emission within the dipole layer plays critical role for helping recombination of electrons and holes. Meanwhile, the insignificant homotandem open-circuit voltage (V oc) loss dependence on dipole layer thickness shows that the quantum tunneling effect is weak for efficient electron and hole recombination. Based on this ICL, poly(3-hexylthiophene) (P3HT)-based homotandem OSC with 1.20 V V oc and 3.29% power conversion efficiency (PCE) is achieved. Furthermore, high efficiency poly(4,8-bis(5-(2-ethylhexyl)-thiophene-2-yl)-benzo[1,2-b54,5-b9]dithiophene-alt alkylcarbonylthieno[3,4-b]thiophene) (PBDTTT-C-T)-based homotandem OSC with 1.54 V V oc and 8.11% PCE is achieved, with almost 15.53% enhancement compared to its single cell. This metal oxide/dipole layer/metal oxide ICL provides a new strategy to develop other qualified ICL with different hole transporting layer and electron transporting layer in tandem OSCs. http://onlinelibrary.wiley.com/doi/10.1002/aenm.201500631/abstract;jsessionid=2900183B20492C6AD4DC4B9F09F856DA.f02t04?deniedAccessCustomisedMessa ge=&userIsAuthenticated=false dipole layer; interconnecting layer; organic solar cell; tandem solar cell
11/04/14 16:55 SKP5050 Effect of Nitric Acid Concentration on Doping of Thin Film Single-walled Carbon Nanotubes for Electrode Application in Transparent, Flexible Dye Sensitized Solar Cells Liling Zhang, Manohar Rao, Jinesh Kochupurackal, Nripan Mathews, Yeng Ming Lam and Subodh G. Mhaisalkar MRS Procee dings (1436), 2013 2013 A simple method is proposed for the chemical modification of carbon nanotubes (CNT) thin film counter electrodes (CE) for the replacement of fluorine-doped tin oxide (FTO) and platinum catalyst (Pt) while retaining light transparency. In order to decrease the sheet resistance, CNT thin films underwent various concentrations (‰ä¤10 M) and durations of HNO3 treatment prior to cell fabrication, and the effect on thin film properties was analyzed. P-doping was observed, and the maximum change in work function was found to be +0.35 eV with 4 M HNO3. Optimum sheet resistance reduction (50%) and work function increment were achieved after 1 h treatment with 4 M HNO3. Changes in optical transmittances for all samples were negligible (å± 5%). Pristine and HNO3 treated films on plastic substrates were tested as CE in flexible bifacial dye sensitized solar cells (DSSC). Most significant improvements in conversion efficiencies were obtained when CNT on plastic substrates were pretreated with 8 M HNO3 (from 1.18% to 1.40% under roomlight, from 0.19% to 0.26% under 1 Sun). http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8820445&fileId=S1946427412017666 devices, transparent conductor, spray deposition
01/05/15 12:20 SKP5050 Interface modification and trap-type transformation in Al-doped CdO/Si-nanowire arrays/p-type Si devices by nanowire surface passivation Yow-Jon Lin, Wei-Min Cho, Hsing-Cheng Chang and Ya-Hui Chen Current Applied Physics (15:3), 2015, pp. 213-218. Mar-15 The present work reports the fabrication and detailed electrical properties of Al-doped CdO/Si-nanowire (SiNW) arrays/p-type Si Schottky diodes with and without SiNW surface passivation. It is shown that the interfacial trap states influence the electronic conduction through the device. The experimental results demonstrate that the effects of the dangling bonds at the SiNW surface and Si vacancies at the SiOx/SiNW interface which can be changed by the Si‰ÛÒO bonding on the energy barrier lowering and the charge transport property. The induced dominance transformation from electron traps to hole traps in the SiNWs by controlling the passivation treatment time is found in this study. http://www.sciencedirect.com/science/article/pii/S1567173914004076 defects, semiconductors; Passivation; Electrical properties, nanostructures
1/14/2015 11:22:22 SKP5050 Fe3W3C/WC /Graphitic Carbon Ternary Nanojunction Hybrids for Dye-Sensitized Solar Cells Dr. Yongping Liao, Prof. Ying Xie, Prof. Kai Pan, Prof. Guofeng Wang, Prof. Qingjiang Pan, Prof. Wei Zhou, Prof. Lei Wang, Prof. Baojiang Jiang and Prof. Honggang Fu ChemSusChem, 2015 Jan-15 Fe3W3C/WC /graphitic carbon (GC) ternary nanojunction hybrids are synthesized through a solid-state pyrolysis process for dye-sensitized solar cells (DSSCs). First-principles calculations have been first employed to investigate the adsorption energy between I3‰öÕ and Fe3W3C and WC nanoclusters. Scanning Kelvin probe images indicate that the work function changes greatly due to the formation of ternary nanojunctions, which favor fast photoelectron transfer. A photoelectrical conversion efficiency of 7.1‰Ûä% is achieved based on Fe3W3C/WC/GC hybrid counter electrodes, which is much higher than those of pure GC (5.02‰Ûä%) and WC/GC hybrids (6.11‰Ûä%). It has been further revealed that Fe3W3C/WC/GC hybrid counter electrodes exhibit the best catalytic performances according to relevant electrochemical measurements, which can be attributed to fast photoelectron transfer due to the ternary junctions and the addition of Fe3W3C with more catalytic metallic atoms. http://onlinelibrary.wiley.com/doi/10.1002/cssc.201402654/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false cyclic voltammetry, electrochemistry, electron microscopy, energy conversion, nanostructures
11/04/14 14:30 SKP5050 Highly efficient electron injection from Indium Tin Oxide/Cross-Linkable Amino-Functionalized Polyfluorene Interface in Inverted Organic Light Emitting Devices Chengmei Zh ong, Shengjian Liu, Fei Huang, Hongbin Wu and Yong Cao Chemistry of Materials (23:21), 2011, pp. 4870-4876 Oct-11 We show that a series of solution processable and cross-linkable amino-functionalized polyfluorene materials can effectively enhance the electron injection from the indium tin oxide (ITO) electrodes, and for the first time, highly efficient inverted organic light emitting devices are fabricated using cross-linkable conjugated polymers as a single electron injection layer without the need for n-type metal oxide layers. The mechanism for the electron injection enhancement effect of the ITO/cross-linkable conjugated polymer interface is studied by X-ray photoelectron spectroscopy, Kelvin probe, and photovoltaic measurement. It was found that the amino groups among these polymers can effectively lower the work function of ITO, which will greatly enhance the electron injection in the resulting devices. http://pubs.acs.org/doi/abs/10.1021/cm2025685 cross-linkable conjugated polymers, inverted structure, organic light-emitting diodes, electron injection layer
1/13/2014 14:36:00 RHC 020 On the correlation between surface morphology and electron work function of indium tin oxide Mingshan Xue, Hainan Wu, Junfei Ou, Fajun Wang, Xibao Li, Wen Li, and Zhonghao Jiang J. Appl. Phys. 111, 123714 (2012) 2013 The electron work function (EWF) is an important parameter of a semiconductor. The understanding of the correlation between the EWF and surface morphology is of much significance for revealing related photoelectric mechanisms. In this study, the surface of indium tin oxide (ITO) was treated by chemical corrosion or absorption of copper phthalocyanine molecules, and their changes in EWF were systematically investigated using scanning Kelvin probe. The decrease of the EWF with the increase of surface roughness was found. Based on a microcapacitor model, the correlation between the EWF and surface microstructures was built up, which was well consistent with the experimental results. These data are of help for improving the photoelectric behaviors of ITO-based devices by adjusting surface/interface structures. http://scitation.aip.org/content/aip/journal/jap/111/12/10.1063/1.4730388 corrosion, surface structure, double layers, surface morphology, electrodes, oxide surfaces, surface oxidation, thin film growth, solid surfaces, surface measurements
1/13/2014 14:33:24 RHC 020 Influence of relative humidity and ozone on atmospheric silver corrosion R. Wiesinger, I. Martina, Ch. Kleber, M. Schreiner Corrosion Science, Volume 77, December 2013, Pages 69‰ÛÒ76 2013 The interaction of highly pure polycrystalline silver samples with ozone (500 ppb) was investigated under certain relative humidity (RH) content (0%, 50% and 90%) in synthetic air. All experiments were performed at room temperature (22 å¡C) and atmospheric pressure. Highly surface sensitive methods were used to investigate chemical, morphological and structural changes and composition of the corrosion products formed at different RH and reaction times. Silver is oxidized by ozone forming Ag2O/AgO(AgIAgIIIO2) surface species. The oxide formation and corrosion rate is dependent on the RH content in the atmosphere, showing that silver is most susceptible to ozone oxidation at 50% RH. http://www.sciencedirect.com/science/article/pii/S0010938X13003387 corrosion, polycrystalline silver, ozone oxidation
02/06/14 17:01 RHC020 Research on the Corrosion Behavior of TC4 Titanium Alloy by Scanning Kelvin Probe Yun Long Ai Advanced Materials Research, 774-776, 699 2013 The corrosion behavior and corrosion morphology of two typical TC4 titanium alloy with equiaxed structure and widmanstatten structure in hydrochloric acid solution were studied using scanning Kelvin probe techniques and observed by scanning electron microscope, respectively. The results show that along with the ongoing of corrosion, surface potential of equiaxed structure alloy is moving to positive direction and that of widmanstatten structure alloy is moving to negative direction after positive direction movement. The surface potential of two kinds structure alloy all present cathode and anode region in the corrosion process, which shows the characteristic of selective corrosion. Surface potential difference of widmanstatten structure alloy is greater than that of equiaxed structure alloy and its corrosion resistance is inferior to that of equiaxed structure alloy. Corrosion preferentially occurs in alpha phase of the two kinds structure alloy through corrosion morphology observation analysis. http://www.scientific.net/AMR.774-776.699 Corrosion Resistance, Scanning Kelvin Probe, Surface Potential, TC4 Titanium Alloy
02/06/14 17:11 RHC020 Research on the Corrosion Behavior of TC4 Titanium Alloy by Scanning Kelvin Probe Yun Long Ai, Li Liu, Wen He Advanced Materials Research (Volumes 774 - 776) 2013 The corrosion behavior and corrosion morphology of two typical TC4 titanium alloy with equiaxed structure and widmanstatten structure in hydrochloric acid solution were studied using scanning Kelvin probe techniques and observed by scanning electron microscope, respectively. The results show that along with the ongoing of corrosion, surface potential of equiaxed structure alloy is moving to positive direction and that of widmanstatten structure alloy is moving to negative direction after positive direction movement. The surface potential of two kinds structure alloy all present cathode and anode region in the corrosion process, which shows the characteristic of selective corrosion. Surface potential difference of widmanstatten structure alloy is greater than that of equiaxed structure alloy and its corrosion resistance is inferior to that of equiaxed structure alloy. Corrosion preferentially occurs in alpha phase of the two kinds structure alloy through corrosion morphology observation analysis. http://www.scientific.net/AMR.774-776.699 Corrosion Resistance, Scanning Kelvin Probe, Surface Potential, TC4 Titanium Alloy
11/05/14 15:34 RHC020 The Corrosion Resistance Discrimination of TC11 Titanium Alloy Using Scanning Kelvin Probe Yun Long Ai, Li Liu and Wen He Advanced Materials Research (815), 2013, pp. 712-716 Oct-13 Surface potential of TC11 titanium alloy handled by beta phase (1150å¡C) solid solution for one hour and then taking water cooling, air cooling and furnace cooling as cold method were investigated using scanning Kelvin probe technique. The corrosion resistance difference of samples was analyzed through their surface potential. At the same time, corrosion experiments were adopted to verify it. The results show that the result of the samples corrosion resistance analyzed by scanning Kelvin probe technique is reliable and the method is feasible. Compared with water cooling sample, the corrosion resistance of furnace cooling and air cooling samples is worse and their surface potential present cathode and anode area obviously. The corrosion of furnace cooling sample is slight serious to that of air cooling sample in the early corrosion, but their corrosion resistances are almost equal. Passivation layer formed by alloy elements in the water cooling sample avails to prevent alloy from corrosion. http://www.scientific.net/AMR.815.712 Corrosion Resistance, Scanning Kelvin Probe, Surface Potential, TC11 Titanium Alloy
02/06/14 17:08 RHC020 On the correlation between surface morphology and electron work function of indium tin oxide Xue, Mingshan Wu, Hainan ; Ou, Junfei ; Wang, Fajun Journal of Applied Physics (Volume:111, Issue: 12 ) 2012 The electron work function (EWF) is an important parameter of a semiconductor. The understanding of the correlation between the EWF and surface morphology is of much significance for revealing related photoelectric mechanisms. In this study, the surface of indium tin oxide (ITO) was treated by chemical corrosion or absorption of copper phthalocyanine molecules, and their changes in EWF were systematically investigated using scanning Kelvin probe. The decrease of the EWF with the increase of surface roughness was found. Based on a microcapacitor model, the correlation between the EWF and surface microstructures was built up, which was well consistent with the experimental results. These data are of help for improving the photoelectric behaviors of ITO-based devices by adjusting surface/interface structures. http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=6225551&abstractAccess=no&userType=inst corrosion indium compounds photoelectricity semiconductor materials surface morphology surface roughness surface treatment work function
1/13/2014 14:54:07 * Secondary electron yield on cryogenic surfaces as a function of physisorbed gases Asena Kuzucan, Holger Neupert, Mauro Taborelli, and Herbert Stoeri J. Vac. Sci. Technol. A 30, 051401 (2012) 2012 Electron cloud is an important limitation for the operation of particle accelerators with intense positively charged beams and short bunch spacing. It occurs if the secondary electron yield (SEY) of the beam-pipe inner wall is sufficiently high to promote electron multiplication. At low temperatures SEY is strongly influenced by the physisorbed gases and by the corresponding surface coverage. These conditions are relevant in accelerators operating with superconducting magnets and cold vacuum sections, such as for instance the Large Hadron Collider. This work investigated the variation of SEY of copper,aluminum, and electropolished copper as a function of physisorbed N2, CO, CO2, CH4, Kr, and C2H6 at cryogenic temperatures. The results of the various gases are compared in order to find a rationale for the behavior of the secondary electrons for various adsorbates. http://scitation.aip.org/content/avs/journal/jvsta/30/5/10.1116/1.4736552 copper, adsorbates, carbon dioxide, secondary emission, adsorption, aluminium, surface photoemission, cryogenics, work functions, electron surface collisions
6/16/2015 11:38:13 KP020 Effect of side chain arrangement of conjugated polyelectrolytes buffer layer on the photovoltaic properties Mi Young Jo, Ye Eun Ha, Yong Sun Won, Seong Il Yoo, Joo Hyun Kim Organic Electronics, 2015 2015 Conjugated polymer electrolytes (CPEs) are well known materials for reducing the electron injection/collection barrier at the cathode interface by the formation of favorable interface dipole. Regardless of their potential applications as a cathode buffer layer (CBL), the effect of the arrangement of side chains with ionic groups of CPEs on photovoltaic properties is not yet fully investigated. In this research, a series of cationic CPEs based on phenothiazine and fluorene, poly[9,9-bis(6-(N,N,N-trimethylammonium)-hexyl)-9H-fluorene] bromide (PHF), poly[9,9-dihexyl-9H-fluorne-alt-9,9-bis(6-(N,N,N-trimethylammonium)-hexyl)-9H-fluorene] bromide (PHcoF), poly[10-(4-(N,N,N-trimetylammonium)-butyl)-10H-phenothiazine-alt-9,9-bis(6-(N,N,N-trimethylammonium)-hexyl)-9H-fluorene] bromide (PTF), and poly[10-butyl-10H-phenothiazine-alt-9,9-bis(6-(N,N,N-trimethylammonium)-hexyl)-9H-fluorene] bromide (PTcoF) have been applied as CBL materials to demonstrate how the arrangement of side chains with quaternary ammonium bromide (QAB) influences photovoltaic properties. PHF and PTF have QABs on every side chain; whereas, PHcoF and PTcoF have QABs on the side chains alternatively. According to the DFT calculation, the conformation of backbone based on fluorene (PHF and PHcoF) is expected to be not exactly in a zigzag conformation, while the zigzag conformation is expected for the alternated copolymers based on phenothiazine and fluorene (PTF and PTcoF). Thus, a number of accumulated QABs by the spontaneous rearrangement of side chains of PHF and PTcoF at the surface of Al electrode will be bigger than that of PHcoF and PTF. A larger number of accumulated QABs at the interface between the thin film of CPEs and the Al electrode leads to a bigger net induced dipole moment by the accumulated QABs, indicating a larger reduction of the effective WF of the Al cathode and reduction of a Schottky barrier at the cathode interface. As a result, the performances of PSCs with PHF and PTcoF as a CBL are better than those of the device with PHcoF and PTF. http://www.sciencedirect.com/science/article/pii/S1566119915002621 Conjugated polymer electrolyte; Side chain arrangement; Cathode buffer layer; Polymer solar cell
01/09/15 11:04 SKP5050 Low band-gap benzodithiophene-thienothiophenecopolymers: the effect of dual two-dimensional substitutions on optoelectronic properties Zhulin Liu, Ji angman Sun, Yongxiang Zhu, Peng Liu, Lianjie Zhang, Junwu Chen, Fei Huang and Yong Cao Science China Chemistry, 2014 Dec-14 Two new conjugated copolymers, PBDT-T6-TTF and PBDT-T12-TTF, were derived from a novel 4-fluorobenzoyl thienothiophene (TTF). In addition, two types of benzodithiophene (BDT) units with 2,3-dihexylthienyl (T6) and 2,3-didodecylthienyl (T12) substituents, respectively, were successfully synthesized. The effect of the dual two-dimensional (2D) substitutions of the building blocks upon the optoelectronic properties of the polymers was investigated. Generally, the two polymers exhibited good solubility and broad absorption, showing similar optical band gaps of ‰ö¼1.53 eV. However, PBDT-T6-TTF with its shorter alkyl chain length possessed a larger extinction coefficient in thin solid film. The highest occupied molecular orbital (HOMO) level of PBDT-T6-TTF was located at ‰öÕ5.38 eV while that of PBDT-T12-TTF was at ‰öÕ5.51 eV. In space charge-limited-current (SCLC) measurement, PBDT-T6-TTF and PBDT-T12-TTF displayed respective hole mobilities of 3.0Ì—10‰öÕ4 and 1.6Ì—10‰öÕ5 cm2 V‰öÕ1s‰öÕ1. In polymer solar cells, PBDT-T6-TTF and PBDT-T12-TTF showed respective power conversion efficiencies (PCEs) of 2.86% and 1.67%. When 1,8-diiodooctane (DIO) was used as the solvent additive, the PCE of PBDT-T6-TTF was remarkably elevated to 4.85%, but the use of DIO for the PBDT-T12-TTF-blend film resulted in a lower PCE of 0.91%. Atomic force microscopy (AFM) indicated that the superior efficiency of PBDT-T6-TTF with 3% DIO (v/v) should be related to the better continuous phase separation of the blend film. Nevertheless, the morphology of the PBDT-T12-TTF deteriorated when the 3% DIO (v/v) was added. Our results suggest that the alkyl-chain length on the 2D BDT units play an important role in determining the optoelectronic properties of dual 2D BDT-TT-based polymers. http://link.springer.com/article/10.1007/s11426-014-5223-7 conjugated copolymers, benzodithiophene, thienothiophene, dual 2-dimentional substitutions, alkyl side-chain length
01/08/15 16:28 SKP5050 Low band-gap benzodithiophene-thienothiophenecopolymers: the effect of dual two-dimensional substitutions on optoelectronic properties Zhulin Liu, Ji angman Sun, Yongxiang Zhu, Peng Liu, Lianjie Zhang, Junwu Chen, Fei Huang, Yong Cao Science China Chemistry Dec-14 Two new conjugated copolymers, PBDT-T6-TTF and PBDT-T12-TTF, were derived from a novel 4-fluorobenzoyl thienothiophene (TTF). In addition, two types of benzodithiophene (BDT) units with 2,3-dihexylthienyl (T6) and 2,3-didodecylthienyl (T12) substituents, respectively, were successfully synthesized. The effect of the dual two-dimensional (2D) substitutions of the building blocks upon the optoelectronic properties of the polymers was investigated. Generally, the two polymers exhibited good solubility and broad absorption, showing similar optical band gaps of ‰ö¼1.53 eV. However, PBDT-T6-TTF with its shorter alkyl chain length possessed a larger extinction coefficient in thin solid film. The highest occupied molecular orbital (HOMO) level of PBDT-T6-TTF was located at ‰öÕ5.38 eV while that of PBDT-T12-TTF was at ‰öÕ5.51 eV. In space charge-limited-current (SCLC) measurement, PBDT-T6-TTF and PBDT-T12-TTF displayed respective hole mobilities of 3.0Ì—10‰öÕ4 and 1.6Ì—10‰öÕ5 cm2 V‰öÕ1s‰öÕ1. In polymer solar cells, PBDT-T6-TTF and PBDT-T12-TTF showed respective power conversion efficiencies (PCEs) of 2.86% and 1.67%. When 1,8-diiodooctane (DIO) was used as the solvent additive, the PCE of PBDT-T6-TTF was remarkably elevated to 4.85%, but the use of DIO for the PBDT-T12-TTF-blend film resulted in a lower PCE of 0.91%. Atomic force microscopy (AFM) indicated that the superior efficiency of PBDT-T6-TTF with 3% DIO (v/v) should be related to the better continuous phase separation of the blend film. Nevertheless, the morphology of the PBDT-T12-TTF deteriorated when the 3% DIO (v/v) was added. Our results suggest that the alkyl-chain length on the 2D BDT units play an important role in determining the optoelectronic properties of dual 2D BDT-TT-based polymers. http://link.springer.com/article/10.1007/s11426-014-5223-7 conjugated copolymers benzodithiophene thienothiophene dual 2-dimentional substitutions alkyl side-chain length
02/10/15 09:45 * Tailoring the Electronic Properties of Colloidal Quantum Dots in Metal‰ÛÒSemiconductor Nanocomposites for High Performance Photodetectors F. Pelayo Gar cÌ­a de Arquer, Tania Lasanta, MarÌ­a Bernechea and Gerasimos Konstantatos Small, 2015 2015 Metallic nanoparticles tailor the electronic properties of PbS colloidal quantum dots in a post-synthetic, all solution-processable approach. The Fermi level of the resulting nanocomposites can be tuned from p- to n-type due to remote charge transfer and electron trap state passivation. This concurrently reduces dark current, improves time response, and increases sensitivity in PbS photoconductors, yielding an over-two-fold increase in detectivity. http://onlinelibrary.wiley.com/doi/10.1002/smll.201403359/abstract;jsessionid=F848E78FE55D615F3FC80D49D7E07CE1.f02t01?deniedAccessCustomisedMessage =&userIsAuthenticated=false colloidal quantum dots, doping, photodetection, plasmonics, metal nanoparticles, nanocomposites
1/13/2014 14:31:48 SPV Kelvin Probe studies of alkyl monolayers on silicon (111) for surface passivation Nicholas Ald erman, Lefteris Danos, Martin C. Grossel and Tom Markvart RSC Adv., 20 13,3, 20125-20131 2013 A chlorination‰ÛÒalkylation procedure has been investigated with a view to improving the surface passivation properties on silicon. We have found that increasing surface coverage of the alkylmonolayer raises the measured SPV and recombination lifetime. A logarithmic trend is observed between the SPV and recombination, showing that monolayer preparation is an important factor in determining the lifetimes observed. The high SPVs measured by Kelvin probe suggest the presence of a silicon surface with a lower concentration of electrons, reducing surface recombination. http://pubs.rsc.org/en/Content/ArticleLanding/2013/RA/C3RA42526F chlorination‰ÛÒalkylation, surface passivation, recombination lifetime
1/13/2014 14:51:00 SPV Large surface photovoltages observed at methyl terminated silicon surfaces synthesised through a two-step chlorination-alkylation method Nicholas Alderman, Lefteris Danos, Martin C. Grossel and Tom Markvart RSC Adv., 20 12,2, 7669-7672 2012 Methylatio of the silicon surface through a chlorination-alkylation method has been used to improve the electronic properties of silicon. Upon alkylation of the surface, an increase in the minority carrier recombination lifetime and the surface photovoltage is observed, in line with an increase in surface charge. A likely explanation of this unusually large band bending is charge accumulation during the removal of chlorine from the surface. http://pubs.rsc.org/en/content/articlelanding/2012/RA/c2ra20465g chlorination-alkylation method, recombination lifetime
1/13/2014 14:54:52 SKP 5050 Charge transport and Kelvin Probe study of organic semiconductor hetero-junction Arvind Kumar, Soumen Samanta, Ajay Singh, A. K. Debnath, R. Prasad, D. K. Aswal, and S. K. Gupta AIP Conf. Proc. 1451, pp. 286-288 (2012) 2012 We have synthesized organic hetero-junction comprising of n-type copper hexadecafluorophthalocyanine (F16CuPc) / p-type cobalt phthalocyanine (CoPc) using molecular beam epitaxy (MBE). The current - voltage (J-V) characteristics of hetero-junction are ohmic in the entire bias range (0-100 V), while individual films shows a transition from ohmic to space charge limited conduction with increasing bias. Hetero-junction shows one order of magnitude higher current density than individual F16CuPc and CoPc films, indicating the formation of a charge accumulation layers at the interface. The thickness of charge accumulation regions was found to be ‰ö¼ 16 nm using Kelvin Probe (KP) method. http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.4732443 charged currents, metallic thin films, molecular beam epitaxy, cobalt, copper, current density, electrical properties, organic semiconductors
1/13/2014 15:02:48 SKP 5050 Energy structure of thin films of carbazole derivatives with metal electrodes K.Pudzs, I.M uzikante, E.Fonavs, J.Simokaitiene, S.Grigalevicius, J.V.Grazilevicius IOP Conf. Series: Materials Science and Engineering 23 (2011) 012020 2011 Study of charge carrier transport in organic electroluminescent devices, organic photovoltaic devices, and organic field-effect transistors is one of the most important points. In order to realize comparable electron and hole transport in thin organic films with electrodes the energy structure of such devices are of great importance. In this work, we have studied electrical properties and energy structure of two carbazole derivatives. The threshold energy of photoconductivity quantum efficiency is 2.90 eV and optical energy gap is 3.3 eV in thin films is obtained. The values of work function of ITO, Au, Cu and Pd electrodes are energetically close to conductivity level of holes and holes injection dominates from electrodes. In these thin films local trapping states of holes are situated at holes conducting level. When electrode is Al layer the local shallow trapping states for electrons at Et = 0.10 eV for compound 1 and at Et = 0.18 eV for compound 2 are determined. http://iopscience.iop.org/1757-899X/23/1/012020 charge carrier transport, organic electroluminescent devices, organic photovoltaic devices, organic field-effect transistors, thin organic films
01/06/15 10:03 RHC020 Enhanced superhydrophilicity and thermal stability of ITO surface with patterned ceria coatings Mingshan Xue, Na Peng, Changquan Li, Junfei Ou, Fajun Wang and Wen Li Applied Surface Science (329), 2015, pp.11-16 Feb-15 Surface wett ability of solid materials is significant for both fundamental research and engineering applications. Compared with most existing fabrication methods of superhydrophilic surfaces by UV exposure or chemical modification, in this work, a superhydrophilic ceria coating on ITO substrate is developed by a fast, simple one-step method. It is found that the superhydrophilicity of ceria coatings is strongly dependent on both the patterned microstructures benefiting the capillary effect and the peculiar chemical composition of ceria inducing numerous oxygen vacancies and large surface free energy. Owing to the inherent physical stability of ceria, such a superhydrophilic ceria coating exhibits an excellently thermal stability at both room temperature and higher temperature. These results open up new avenues for the underlying applications of superhydrophilic coatings, such as heat transfer/dissipation. http://www.sciencedirect.com/science/article/pii/S0169433214028712 Ceria coatings, superhydrophilicity, thermal stability
1/13/2014 14:43:05 SKP 5050 Work function of colloidal semiconducting nanocrystals measured by Kelvin probe P Kulis, J Buti kova, B Polyakov, G Marcins, J Pervenecka, K Pudzs, I Tale IOP Conf. Series: Materials Science and Engineering 38 (2012) 012048 2012 Colloidal suspensions of CdS, PbS, Cu2S, Ag2S and ZnO nanocrystals were prepared by chemical route in presence of organic capping ligands. The formation of nanocrystals was studied by using UV-visible absorption spectroscopy. Kelvin probe measurements of work function were performed on nanocrystals thin film on ITO (indium tin oxide) coated glass. http://iopscience.iop.org/1757-899X/38/1/012048 CdS, PbS, Cu2S, Ag2S, ZnO, nanocrystals, thin films, ITO
11/05/14 11:58 KP020 Efficient polymer bulk heterojunction solar cells with cesium acetate as the cathode interfacial layer Yuehua Jia, L iying Yang, Wenjing Qin, Shougen Yin, Fengling Zhang and Jun Wei Renewable Energy (50), 2013, pp.565-569. Feb-13 The enhanced performance of polymer solar cells based on regioregular poly(3-hexylthiophene) (P3HT) and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend was achieved by using cesium acetate (CH3COOCs) as cathode buffer layer. Under 100 mW/cm2 white light illumination, the device with 0.8 nm thick CH3COOCs as cathode buffer layer exhibits power conversion efficiency (PCE) as high as (4.16 å± 0.02) %. Compared to the control devices without cathode buffer layer and with LiF as cathode buffer layer, the PCE is enhanced ‰ö¼100% and ‰ö¼31%, respectively. The introduction of the CH3COOCs buffer layer effectively improves the photo-generated charge collection. The Kelvin Probe measurement shows that the work function of the CH3COOCs is estimated to be ‰öÕ4.0 eV, which has an ideal energy band match with PCBM and a good property for electron collection. The static contact angle results indicated that the CH3COOCs with the hydrophobic CH3COO- group has an improved wettability between the buffer layer and the hydrophobic organic active layer surface, resulting in better interfacial contact and reduced contact resistance. The improved performance may be attributed to the dissociation of semi-conducting CH3COOCs upon deposition to liberate Cs with a low work function, which reduces the interface resistance of the active layer and the cathode and enhances the interior electric field that may result in efficient charge transportation. Therefore, the CH3COOCs interlayer could be a promising alternative to LiF to improve the efficiency of the electron collection of polymer bulk heterojunction solar cells. http://www.sciencedirect.com/science/article/pii/S0960148112004387 Cathode buffer layer; Cesium acetate; Polymer bulk heterojunction; Polymer solar cells; Interlayer
02/03/15 14:26 SKP5050 Alternative Carrier Injection/Extraction Inspired by Electrode Interlayers Based on Peripheral Modification of the Electron-Rich Skeleton Dongcheng Chen, Chongyang Zhang, Hu Zhou, Xinchao Li, Zhiheng Wang, Shi-Jian Su and Yong Cao ACS Applied Materials and Interfaces, 2015 Jan-15 Peripheral modifications of the electron-rich trifluorene-substituted triphenylamine core have been comparatively studied through the linkage of the different polar pendants with fluorene via saturated sp3 hybrid alkyl chains. The work function of electrode could be effectively tuned by the interlayers with or without peripheral pendants of phosphoric acid and phosphonate groups to give selective hole and electron injection/extraction property. Their applications in various vacuum- and solution-processed organic light-emitting diodes and photovoltaic devices were thoroughly investigated. The current comparative study provides valuable exploration on developing high-performance environmentally friendly solvent-processed electrode interlayer materials. http://pubs.acs.org/doi/abs/10.1021/am507429j carrier injection/extraction; organic/polymer light-emitting diodes; polymer solar cells; environment-friendly; electrode interlayers
4/22/2014 10:47:35 RHC020 Photoactivated titania-based nanomaterials for potential application as cardiovascular stent coatings Marta Kopaczyãskaa, Corresponding author contact information, E-mail the corresponding author, Beata Sobieszczaãskab, Agnieszka Ulatowska-Jar¼aa, Iwona Hoâowacza, Igor Buzalewicza, ukasz Wasylukf, Syed A.M. Tofaile, Dariusz Biaâyc, Magdalena Wawrzyãskad, Halina Podbielskaa Biocybernetics and Biomedical Engineering Apr-14 Intravascular stenting of atherosclerotic coronary arteries is a life-saving, widely used procedure in interventional cardiology. Adverse clinical outcomes such as restenosis highlight the importance of meeting the excellent biocompatibility by cardiovascular implants. Many attempts have been made to improve the safety profile of implant surface. We for the first time developed the photoactive intravascular titania-based nanomaterials for the application as cardiovascular stent coating. Photoactive biomaterial deposited on the cardiovascular stent surface demonstrated promising features, making it an excellent substrate for endothelial cells growth and proliferation. The biocompatibility of these coatings has been compared with 316L stainless steel surfaces typically used in commercial coronary stents production. The results of the study proved that the innovative titania-based coatings have better biocompatibility characteristics than the 316L stainless steel and in regard of its antithrombotic potential provided protection against restenosis. Furthermore, the titania coating supported endothelial cells attachment and proliferation, and induced prolonged plasma recalcification time in comparison with stainless steel surface. Innovative photoactive titania coating can be an important factor to prevent the process of the restenosis in the place of implantation. http://www.sciencedirect.com/science/article/pii/S020852161400028X Cardiovascular stent; Photoactive coating; Endothelial cells; Surface charge; Biocompatibility
3/19/2015 9: 08:14 SKP505 Photoelectrochemical Hydrogen Generation Using C-dot/ZnO Hierarchical Nanostructure as an Efficient Photoanode Heejin Kim, Woosung Kwon, Mingi Choi, Shi-Woo Rhee and Kijung Yong Journal of the Electrochemical Society, 2015 Mar-15 In this study, we have developed a stable and environmental-friendly photoelectrode of carbon nanodots (C-dots) coupled with a 3 dimensional ZnO structure. Our C-dots are synthesized hydrothermally with a high yield of 40%, and they are successfully anchored onto the ZnO backbone via a facile solution procedure. The as-prepared C-dot/ZnO photoelectrodes have exhibited reasonable photocurrent density and remarkable photostability under the 1 sun irradiation condition without any sacrificial reagent. We have studied the chemistry beneath the C-dot/ZnO interface through various spectroscopic and electrochemical techniques. This work could shed light on future application of C-dots in efficient and toxin-free solar water-splitting systems. http://jes.ecsdl.org/content/162/6/H366.short carbon nanodot; photoelectrochemical hydrogen generation; ZnO nanorod
11/05/14 09:08 SKP5050 Energy structure and electro-optical properties of organic layers with carbazole derivative K. Pudzsa, A. Vembris, I. Muzikante, R. Grzibovskis, B. Turovska, J. Simokaitiene, S. Grigalevicius, J.V. Grazulevicius Thin Solid Films (556), 2014, pp. 405-409 Apr-14 Phosphorescent organic light emitting diodes are perspective in lighting technologies due to high efficient electroluminescence. Not only phosphorescent dyes but also host materials are important aspect to be considered in the devices where they are a problem for blue light emitting phosphorescent molecules. Carbazole derivative 3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole (TCz1) is a good candidate and has shown excellent results in thermally evaporated films. This paper presents the studies of electrical properties and energy structure in thin films of spin-coated TCz1 and thermally evaporated tris[2-(2,4-difluorophenyl)pyridine]iridium(III) (Ir(Fppy)3). The 0.46 eV difference of electron conduction level between TCz1 and Ir(Fppy)3 compounds was obtained from the cyclic voltammetry and photoconductivity measurements. Temperature modulated space charge limited current (TM-SCLC) method is used to measure the local trapping states for charge carrier in the energy gap. The TM-SCLC measurements for the system TCz1 + 8 wt.% Ir(Fppy)3 show a trapping state with the value of 0.4 eV which is comparable to the conduction level difference of these materials. It allows to conclude that Ir(Fppy)3 molecules act as electron traps in the TCz1 matrix and the TM-SCLC method is applicable to investigate dopants as trapping states. To show the trap effect, an organic light emitting diode was made where the electroluminescent layer was a spin-coated host-guest system of TCz1 with incorporated 8 wt.% Ir(Fppy)3. http://www.sciencedirect.com/science/article/pii/S0040609013020956 Bipolar conductive organic materials; Temperature modulated space charge limited current; Local trapping states; Electroluminescence
1/13/2014 14:43:42 SKP 5050 Applying the Kelvin probe to biological tissues: Theoretical and computational analyses Andrew C. A hn, Brian J. Gow, Ì÷rjan G. Martinsen, Min Zhao, Alan J. Grodzinsky, and Iain D. Baikie Physical Review E 85.6 (2012): 061901 2012 The Kelvin probe measures surface electrical potential without making physical contact with the specimen. It relies on capacitive coupling between an oscillating metal tip that is normal to a specimen's surface. Kelvin probes have been increasingly used to study surface and electrical properties of metals and semiconductors and are capable of detecting material surface potentials with submillivolt resolution at a micrometer spatial scale. Its capability for measuring electrical potential without being confounded by electrode-specimen contact makes extending its use towards biological materials particularly appealing. However, the theoretical basis for applying the Kelvin probe to dielectric or partially conductive materials such as biological tissue has not been evaluated and remains unclear. This study develops the theoretical basis underlying Kelvin probe measurements in five theoretical materials: highly conductive, conductive dielectric with rapid charge relaxation, conductive dielectric with slow charge relaxation, perfect dielectric, and tissue with a bulk serial resistance. These theoretically derived equations are then computationally analyzed using parameters from both theoretical specimens and actual biomaterials-including wet skin, dry skin, cerebrospinal fluid, and tendon. Based on these analyses, a Kelvin probe performs in two distinct ways depending on the charge relaxation rates of the sample: The specimen is treated either as a perfect dielectric or as highly conductive material. Because of their rapid relaxation rate and increased permittivity biomaterials behave similarly to highly conductive materials, such as metal, when evaluated by the Kelvin probe. These results indicate that the Kelvin probe can be readily applied to studying the surface potential of biological tissue. http://www.ncbi.nlm.nih.gov/pubmed/23005121 biological tissue, biomaterials, highly conductive, conductive dielectric, perfect dielectric
1/13/2014 14:36:32 UHV m-BiVO4@ë³ -Bi2O3 core‰ÛÒshell p‰ÛÒn heterogeneous nanostructure for enhanced visible-light photocatalytic performance Mandi Han, Ting Sun, Pei Yun Tan, Xiaofeng Chen, Ooi Kiang Tan and Man Siu Tse RSC Adv., 20 13,3, 24964-24970 2013 In this paper, ë³-Bi2O3, considered as the best photocatalyst among all Bi2O3 polymorphs, was successfully prepared on the surface of m-BiVO4 octahedral crystals through an alkaline ‰ÛÏetching‰Û process. Extensive XRD, SEM and TEM characterization revealed the formation of a p‰ÛÒn junction in the form of m-BiVO4@ë³-Bi2O3 core‰ÛÒshell heterostructure. In addition, the alkaline concentration and reaction time during the etching process were studied and found to be critical parameters in the formation and yield of the Bi2O3 phase. The visible-light photocatalytic activities of these heterogeneous samples with different ë³-Bi2O3/m-BiVO4 phase ratios were evaluated for the degradation of Rhodamine B (RhB). The results indicated that with an optimum amount of ë³-Bi2O3 on the m-BiVO4 surface, the powders showed superior photocatalytic performance over pure m-BiVO4 octahedral crystals. The enhancement mechanisms were discussed based on the specific surface area and ë³-Bi2O3 shell thickness, as well as the influences of improved charge carrier transfer on the p‰ÛÒn heterostructure. http://pubs.rsc.org/en/content/articlelanding/2013/ra/c3ra42870b Bi2O3 polymorphs, characterization, visible-light photocatalytic activities
10/29/2014 10:27:35 SKP5050 Effect of Te doping on the thermopower of PbSe1-xTex Ranita Basu, S. Bhattacharya, Ranu Bhatt, Ajay Singh, D. K. Aswal, S. K. Gupta Emerging Materials Research (1:6), 2012, pp. 306-311 Nov-12 The authors have studied the effect of Te doping on structural, morphological and thermopower of PbSe for the composition of PbSe1‰ÛÒxTex (x = 0åá0, 0åá2, 0åá50, 0åá75, 0åá9 and 1åá0). The samples were prepared using melting and rocking. The scanning electron microscopy indicated that all the samples have lamellar morphology. The X-ray diffraction analysis suggested that the lattice parameter increases linearly with dopant concentration (x). The temperature dependence of thermopower measured for samples having different x revealed unusual increase in thermopower for the composition x = 0åá5, for example, at 427å¡C, and the thermopower values for PbSe0åá5Te0åá5, PbTe and PbSe were 292, 188 and 134 ë¼V/K, respectively. A dramatic thermopower enhancement for PbSe0åá5Te0åá5 is attributed to scattering of the majority charge carriers by the defect sites. http://www.icevirtuallibrary.com/content/article/10.1680/emr.12.00015 band structure, alloys, semiconductor
11/05/14 09:20 SKP5050 XPS study of the band alignment at ITO/oxide (n‰Ûtype MoO3 or p‰Ûtype NiO) interface J. C. Bern̬d e, S. Houari, D. Nguyen, P. Y. Jouan, A. Khelil, A. Mokrani, L. Cattin and P. Predeep physica status solidi (a) May-12 While they have different electronic properties n-type MoO3 and p-type NiO are very efficient as buffer layers between the ITO anode and the organic electron donor in organic photovoltaic cells. While it is admitted that MoO3 is n-type, its band structure is still under study. Here, the band alignment at the interface of an ITO/MoO3 heterojunction is studied by X-ray photoelectron spectroscopy (XPS). The same study is realized on the structure ITO/NiO, NiO being a p-type semiconductor. The measurements have been performed on samples obtained under the same experimental conditions as those used to achieve organic photovoltaic cells. The MoO3 (NiO) upper layer was 3‰Ûänm thick. The semidirect XPS technique used to measure the band offsets allows us to estimate the band discontinuities at the interface ITO/MoO3: ëÓEv‰Ûä=‰Ûä0.50‰ÛäeV and ëÓEc‰Ûä=‰Ûä0.90‰ÛäeV, while at the interface ITO/NiO we have ëÓEv‰Ûä=‰Ûä‰öÕ2.10‰ÛäeV and ëÓEc‰Ûä=‰Ûä‰öÕ1.90‰ÛäeV. Therefore, n-type MoO3 and p-type NiO, which are both very efficient anode buffer layers (ABLs), exhibit different band structure at the contact with ITO. However, the measurement, by means of a Kelvin probe, of the work functions of the structures ITO/NiO and ITO/MoO3, shows that they are close and significantly higher than that of ITO alone. http://onlinelibrary.wiley.com/doi/10.1002/pssa.201127428/abstract;jsessionid=4C876D1927CEBBB0101EC1FD0D784967.f03t02?deniedAccessCustomisedMessag e=&userIsAuthenticated=false band alignment; interfaces; oxides; XPS
1/13/2014 14:30:33 KP Role of a disperse carbon interlayer on the performances of tandem a-Si solar cells Andreia Ara ujo, Raquel Barros, Tiago Mateus, Diana Gaspar, Nuno Neves, Antonio Vicente, Sergej A Filonovich, Pedro Barquinha, Elvira Fortunato, Ana M Ferraria, Ana M Botelho do Rego, Ana Bicho, Hugo Aguas and Rodrigo Martins Sci. Technol. Adv. Mater. 14 (2013) 045009 2013 We report the effect of a disperse carbon interlayer between the n-a-Si:H layer and an aluminium zinc oxide (AZO) back contact on the performance of amorphous silicon solar cells. Carbon was incorporated to the AZO film as revealed by x-ray photoelectron spectroscopy and energy-dispersive x-ray analysis. Solar cells fabricated on glass substrates using AZO in the back contact performed better when a disperse carbon interlayer was present in their structure. They exhibited an initial efficiency of 11%, open-circuit voltage Voc = 1.6 V, short-circuit current JSC = 11 mA cm‰öÕ2 and a filling factor of 63%, that is, a 10% increase in the JSC and 20% increase in the efficiency compared to a standard solar cell. http://iopscience.iop.org/1468-6996/14/4/045009 AZO, amorphous silicon solar cells, x-ray photoelectron spectroscopy
1/13/2014 15:04:22 KP 020 Manganese- doped indium oxide and its application in organic light-emitting diodes Yaqin Liao, Qipeng Lu, Yi Fan, and Xingyuan Liu Appl. Phys. Lett. 99, 023302 (2011) 2011 Thin films of manganese-doped indium oxide (IMO) deposited by electron beam evaporation have been investigated as anodes in organic light-emitting diodes(OLEDs). The IMO films have a high work function of 5.35 eV, a desirable surface morphology with an average roughness of 1.1 nm, a high average optical transmittance of 87.2% in the visible region, and a maximum optical transmittance of 92% at 460 nm. It is demonstrated that an IMO anode can effectively improve hole injection at the anode/organic interface, resulting in OLEDs with an increased electroluminescent efficiency. http://scitation.aip.org/content/aip/journal/apl/99/2/10.1063/1.3610559 anodes, organic light emitting diodes, thin films, surface measurements, electron beam deposition, surface morphology, electrical properties, indium, electrical resistivity, electrodeposition
1/13/2014 14:24:21 SKP 5050 Effects of rapid thermal annealing on electrical, optical, and structural properties of Ni-doped In2O3 anodes for bulk heterojunction organic solar cells Jun Ho Kim and Tae-Yeon Seong; Han-Ki Kim J. Vac. Sci.Technol. A 31(2), Mar/Apr 2013 2013 The authors investigated the effects of rapid thermal annealing (RTA) on the electrical, optical, and structural properties, and work functions of Ni-doped In2O3 (INO) anodes prepared by a DC/RF co-sputtering process for use in bulk heterojunction organic solar cells (OSCs). By RTA processing at 600‰Ûäå¡C, the authors obtained the optimized INO anodes with a sheet resistance of 28 ë©/sq, an optical transmittance of 82.93%, and a work function of 5.02‰ÛäeV, which are acceptable in OSC fabrication. In particular, the 600‰Ûäå¡C annealed INO anode showed much higher optical transmittance in the near infrared wavelength region than the conventional ITOfilm, even though it had a low resistivity of 5.66‰ÛäÌ—‰Ûä10‰öÕ4 ë© cm. The OSC fabricated on theannealed INO anode showed a higher power convention efficiency of 2.65% than the OSC with as-deposited INO anodes (2.19%) because the fill factors of the OSC are critically dependent on the sheet resistance of the anode. http://scitation.aip.org/content/avs/journal/jvsta/31/2/10.1116/1.4774212 anodes, annealing, thin films, work functions, electrical resistivity, ozone, thin film structure, near infrared imaging, optical properties, X-ray diffraction
1/13/2014 14:19:59 SKP 5050 Anisotropy in amorphous films of cross-shaped molecules with an accompanying effect on carrier mobility: Ellipsometric and sum-frequency vibrational spectroscopy studies Masahito Oh -e, Hidenori Ogata, Yoshimasa Fujita, and Mitsuhiro Koden Appl. Phys. Lett. 102, 101905 (2013) 2013 Variable angle spectroscopic ellipsometry and sum-frequency vibrational spectroscopy have been used to study molecular orientations in thin films used in an organic light-emitting-diode. The films consist of sterically bulky and cross-shaped molecules that have small anisotropy in shape, 2-methyl-9,10-di(2-naphthyl)anthracene (MADN). As a result, anisotropic molecular orientation in the amorphous films has been observed with respect to the surface normal. The short axis of anthracene in MADN molecules, more or less, slightly tilts from the surface plane but preferentially close to the surface with a certain orientational distribution, while the long axis of anthracene is, on average, oriented close to the magic angle from the surface normal. Thisanisotropic molecular orientation gives rise to better carrier transportation properties than the isotropic orientation. http://scitation.aip.org/content/aip/journal/apl/102/10/10.1063/1.4792746 anisotropy, polycyclic aromatic hydrocarbons, Fermi surface, transport properties, organic light emitting diodes, thin film devices, ellipsometry, infrared spectra, vibrational spectroscopy, carrier mobility
11/05/14 11:30 KP020 The influence of perpendicular transport behavior on the properties of n-i-p type amorphous silicon solar cells Jun Ma, Jian Ni, Jianjun Zhang, Qun Liu, Guofu Hou, Xinliang Chen, XiaoDan Zhang, Xinhua Geng and Ying Zhao Solar Energy Materials and Solar Cells (120:B), 2014, pp. 635-641. Jan-14 Different types of boron-doped window layers have been prepared by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) at a low temperature of 150 å¡C. The effects of perpendicular transport behavior on the properties of n‰ÛÒi‰ÛÒp type amorphous silicon (a-Si) solar cells, which involve inner perpendicular conductivity of p layers, perpendicular transport properties at p/ITO interfaces and recombination kinetics at i/p interfaces have been investigated by perpendicular dark conductivity, potential barrier at p/ITO and dark current‰ÛÒvoltage characteristics of n-i-p a-Si diodes, respectively. High doping efficiency in the window layers with nano-sized silicon crystals has been observed to facilitate the significant improvement of perpendicular dark conductivity and transport behavior at p/ITO interfaces. The dark current‰ÛÒvoltage characteristics indicated intrinsic a-Si/p-type microcrystalline silicon heterojunction transitions possessed much higher recombination rate and decreased value of built-in potential in the intrinsic layer. By optimizing the process parameters, high open circuit voltage (0.96 V) and fill factor (0.73) were achieved for n-i-p type a-Si single junction solar cell with p-type amorphous silicon carbide/nanocrystalline silicon hybrid window layer. http://www.sciencedirect.com/science/article/pii/S092702481300528X Amorphous silicon; Solar cell; Hybrid window layer; Perpendicular electronic transport; Interfaces
1/13/2014 14:49:39 KP 020 Improvement of the open circuit voltage by modifying the transparent ITO front electrode in amorphous n-i-p solar cells F.-J. Haug, R. Biron, G. Kratzer, F. Leresche, J. Besuchet, C. Ballif, M. Dissel, S. Kretschmer, W. Soppe, P. Lippens, and K. Leitner Progress in photovoltaics: Research and Applications, Volume 20, Issue 6, pages 727‰ÛÒ734, September 2012 2012 At the front contact of thin film silicon solar cells, the junction between the p-doped window layer and the n-type transparent electrode results in a barrier that must be surmounted by the charge carriers. The barrier height is governed by the work-function difference of these two materials. For different compositions of the well known In2O3‰ÛÒSnO2 (ITO) system, we find that higher oxygen partial pressure during sputter deposition increases the work function of the deposited films. Over the same range of oxygen partial pressures, ITO electrodes with low tin content applied to n‰ÛÒi‰ÛÒp type thin film silicon solar yield a gain in VOC by up to 40‰ÛämV. http://onlinelibrary.wiley.com/doi/10.1002/pip.1220/abstract amorphous silicon, solar cells, work function
10/13/2014 12:22:59 SKP5050 Alcohol-soluble polyfuorenes containing dibenzothiophene-S, S-dioxide segments for cathode interfacial layer in PLEDs and PSCs Huiping Xiao, Jingsheng Miao, Jiaqing Cao, Wei Yang, Hongbin Wu, Yong Cao Organic Electronics Jan-14 A series of alcohol-soluble amino-functionalized polyfluorene derivatives (PF-N-S, PF-N-SC8 and PF-N-SOC8) comprising various ratios of dibenzothiophene-S,S-dioxide segments (S/SC8/SOC8) in the main chains, respectively, were synthesized and utilized as cathode interfacial layer (CIL) in polymer light-emitting diodes (PLEDs) and polymer solar cells (PSCs) with high-work-function Al (or Au) electrode. The polymers possess LUMO/HOMO levels at ‰öÕ2.78 to ‰öÕ3.53 eV/‰öÕ5.69 to ‰öÕ6.32 eV. Multilayer PLEDs and PSCs with device configurations of ITO/PEDOT:PSS (40 nm)/P-PPV or PFO-DBT35:PCBM = 1:2 (80 nm)/CIL (3‰ÛÒ15 nm)/Al (or Au) (100 nm) were fabricated. The PF-N-S-10/Al (or Au) cathode PLEDs displayed maximum luminous efficiency of 24.4 cd A‰öÕ1 (or 11.9 cd A‰öÕ1), significantly higher than bare Al (or Au) cathode device, exceeding well-known Ba/Al and poly[(9,9-bis(3‰Û²-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN)/Al (or PFN/Au) cathode devices. The enhanced open-circuit voltages (Vocs), electron reflux and reduced work functions clarify that the electron injection barrier from the Al (or Au) electrode can be lowered by inserting the polymers as CIL. The resulted PSCs also show device performances exceeding Al and PFN/Al cathode devices. The results indicate that PF-N-S, PF-N-SC8 and PF-N-SOC8 are excellent CIL materials for PLEDs and PSCs with high-work-function Al or Au electrode. http://dx.doi.org/10.1016/j.orgel.2014.01.006 Amino-functionalized polyfluorene derivatives, Dibenzothiophene-S, S-dioxide, Cathode interfacial layer, Polymer light-emitting diode, Polymer solar cell
01/06/15 11:24 APS02 Dual Mode Kelvin Probe: Featuring Ambient Pressure Photoemission Spectroscopy and Contact Potential Difference Iain D. Baikie, Angela C. Grain, James Sutherland and Jamie Law Energy Procedia (60), 2014, pp. 48-56. 2014 We describe a novel dual-mode Kelvin probe featuring ambient pressure Photoemission Spectroscopy (PES), which yields information on the absolute work function (ë¦) of a metal and the Ionisation Potential (IP) of a semiconductor, coupled with a high resolution Contact Potential Difference capability which can be extended to Surface Photovoltage measurements. The relative energy resolution are 50 meV for PES and 1-3 meV for CPD. To surmount the limitation of electron scattering in air the incident photon energy is rastered rather than applying a variable retarding electric field as is used UPS. We propose a mechanism of atmospheric ion generation and show that for the metal photoresponse obeys Fowler Theory. The relationship between CPD and photoelectric threshold is a useful tool in characterizing the electrical behavior of materials. We illustrate this with native oxide covered Cu and n-type Si. Further we show that the photoresponse can be used to generate the near Fermi-level Density of States (DOS) in Iron and Nickel-Phthalocyanine. http://www.sciencedirect.com/science/article/pii/S1876610214033712 ambient photoemission spectroscopy; Kelvin Probe; CPD; SPV; PES; Fowler theory, Cu2O, NiPc, FePc
1/13/2014 14:23:08 SKP 5050 Excellent c-Si surface passivation by thermal atomic layer deposited aluminum oxide after industrial firing activation B Liao, R Sta ngl, F Ma, T Mueller, F Lin, A G Aberle, C S Bhatia and B Hoex J. Phys. D: Appl. Phys. 46 385102 2013 We demonstrate that by using a water (H2O)-based thermal atomic layer deposited (ALD) aluminum oxide (Al2O3) film, excellent surface passivation can be attained on planar low-resistivity silicon wafers. Effective carrier lifetime values of up to 12 ms and surface recombination velocities as low as 0.33 cm s‰öÕ1 are achieved on float-zone wafers after a post-deposition thermal activation of the Al2O3 passivation layer. This post-deposition activation is achieved using an industrial high-temperature firing process which is commonly used for contact formation of standard screen-printed silicon solar cells. Neither a low-temperature post-deposition anneal nor a silicon nitride capping layer is required in this case. Deposition temperatures in the 100‰ÛÒ400 å¡C range and peak firing temperatures of about 800 å¡C (set temperature) are investigated. Photoluminescence imaging shows that the surface passivation is laterally uniform. Corona charging and capacitance‰ÛÒvoltage measurements reveal that the negative fixed charge density near the AlOx/c-Si interface increases from 1.4 Ì— 1012 to 3.3 Ì— 1012 cm‰öÕ2 due to firing, while the midgap interface defect density reduces from 3.3 Ì— 1011 to 0.8 Ì— 1011 cm‰öÕ2 eV‰öÕ1. This work demonstrates that direct firing activation of thermal ALD Al2O3 is feasible, which could be beneficial for solar cell manufacturing. http://iopscience.iop.org/0022-3727/46/38/385102/ aluminum oxide, surface passivation, carrier lifetime, silicon solar cells
1/13/2014 14:20:38 SKP5050 The effect of light soaking on crystalline silicon surface passivation by atomic layer deposited Al2O3 Liao, Baochen, Stangl, Rolf, Mueller, Thomas, Lin, Fen, Bhatia, Charanjit S., Hoex, Bram Journal of Applied Physics (Volume 113, Issue 2) 2013 The effect of light soaking of crystalline silicon wafer lifetime samples surface passivated by thermal atomic layer deposited (ALD) Al 2O3 is investigated in this paper. Contrary to otherpassivation materials used in solar cell applications (i.e., SiO2, SiNx), using thermal ALD Al 2O3, an increase in effective carrier lifetime after light soaking under standard testing conditions is observed for both p-type (‰ö¼45%) and n-type (‰ö¼60%) FZ c-Si lifetime samples. After light soaking and storing the samples in a dark and dry environment, the effective lifetime decreases again and practically returns to the value before light soaking. The rate of lifetime decrease after light soaking is significantly slower than the rate of lifetime increase by light soaking. To investigate the underlying mechanism, corona charge experiments are carried out on p-type c-Si samples before and after light soaking. The results indicate that the negative fixed charge density Qfpresent in the Al 2O3 films increases due to the light soaking, which results in an improved field-effect passivation. Numerical calculations also confirm that the improved field-effect passivationis the main contributor for the increased effective lifetime after light soaking. To further understand the light soaking phenomenon, a kinetic model‰ÛÓa charge trapping/de-trapping model‰ÛÓis proposed to explain the time dependent behavior of the lifetime increase/decrease observed under/after light soaking. The trap model fits the experimental results very well. The observed light enhanced passivation for ALD Al 2O3 passivated c-Si is of technological relevance, because solar cell devices operate under illumination, thus an increase in solar cellefficiency due to light soaking can be expected. http://scitation.aip.org/content/aip/journal/jap/113/2/10.1063/1.4775595 aluminium compounds, atomic layer deposition, carrier lifetime, corona, elemental semiconductors, numerical analysis, passivation, silicon solar cells
1/13/2014 14:34:34 SKP + RHC Galvanically Induced Intergranular Corrosion of AA5083-H131 Under Atmospheric Exposure Conditions: Part 2‰ÛÓModeling of the Damage Distribution D. Mizuno a nd R.G. Kelly Corrosion: June 2013, Vol. 69, No. 7, pp. 681-692 2013 In this second in a series of two papers, a computational model to predict intergranular corrosion (IGC) damage caused by galvanic interactions between aluminum alloy (AA)5083 (UNS A95083) and AISI 4340 (UNS G43400) steel is presented. This model calculates the potential distribution based on the tertiary current distribution calculated from the Laplace equation using experimentally derived electrochemical boundary conditions. The potential distribution so derived was used to predict IGC depth after 100 h in solutions of different sodium chloride (NaCl) concentrations and compared to the experimental data presented in Part 1. The model calculations show good agreement with the results from exposure tests over a range of atmospheric conditions. The ability to predict the damage after 100 h using potential distributions calculated without considering any time dependencies, including homogeneous reactions, implies that the ohmic drop associated with the atmospheric exposure condition is of greater importance than changes in thin solution layer chemistry for this system. The influences of the degree of sensitization, relative humidity, and salt loading density on IGC propagation can be described by the model. The assumptions and limitations of the current model are also discussed. http://corrosionjournal.org/doi/abs/10.5006/0813 AA5083, atmospheric corrosion, finite element method, galvanic corrosion, intergranular corrosion, modeling studies, sensitization
02/06/14 17:10 RHC020 Galvanically Induced Intergranular Corrosion of AA5083-H131 Under Atmospheric Exposure Conditions: Part 1‰ÛÓExperimental Characterization D. Mizuno * and R.G. Kelly Corrosion: June 2013, Vol. 69, No. 6, pp. 580-592. 2013 In a two-part series of papers, the galvanic corrosion behavior of sensitized aluminum alloy (AA)5083-H131 (UNS A95083) when coupled with AISI 4340 (UNS G43400) steel was studied experimentally and computationally, with an emphasis on atmospheric conditions. In Part 1, the electrochemical kinetics of AA5083-H131 and steel in salt solutions of relevance to atmospheric corrosion were determined, including the influence of the degree of sensitization (DoS), potential, and sodium chloride (NaCl) concentration in the context of intergranular corrosion (IGC) propagation. More severe IGC was seen on materials with higher degrees of DoS, with damage depths of 1 mm or more developing in 100 h. The extent of IGC damage over 100 h was proportional to potential for a wide range of NaCl concentrations. These results from full immersion were compared with exposure testing and scanning Kelvin probe (SKP) measurements conducted under atmospheric conditions. It was found that the extent and spatial distribution of IGC damage on the atmospherically exposed material corresponded well to the IGC damage distribution expected from the SKP potential measurements and the damage results from the full immersion experiments. These findings are used as the input data for the computational model to predict the IGC damage distribution presented in the second paper. http://www.corrosionjournal.org/doi/abs/10.5006/0812 AA5083-H131, atmospheric corrosion, galvanic corrosion, intergranular corrosion, sensitization
1/13/2014 14:35:22 SKP + RHC Galvanically Induced Intergranular Corrosion of AA5083-H131 Under Atmospheric Exposure Conditions: Part 1‰ÛÓExperimental Characterization D. Mizuno and R.G. Kelly Corrosion: June 2013, Vol. 69, No. 6, pp. 580-592 2013 In a two-part series of papers, the galvanic corrosion behavior of sensitized aluminum alloy (AA)5083-H131 (UNS A95083) when coupled with AISI 4340 (UNS G43400) steel was studied experimentally and computationally, with an emphasis on atmospheric conditions. In Part 1, the electrochemical kinetics of AA5083-H131 and steel in salt solutions of relevance to atmospheric corrosion were determined, including the influence of the degree of sensitization (DoS), potential, and sodium chloride (NaCl) concentration in the context of intergranular corrosion (IGC) propagation. More severe IGC was seen on materials with higher degrees of DoS, with damage depths of 1 mm or more developing in 100 h. The extent of IGC damage over 100 h was proportional to potential for a wide range of NaCl concentrations. These results from full immersion were compared with exposure testing and scanning Kelvin probe (SKP) measurements conducted under atmospheric conditions. It was found that the extent and spatial distribution of IGC damage on the atmospherically exposed material corresponded well to the IGC damage distribution expected from the SKP potential measurements and the damage results from the full immersion experiments. These findings are used as the input data for the computational model to predict the IGC damage distribution presented in the second paper. http://corrosionjournal.org/doi/abs/10.5006/0812 AA5083-H131, atmospheric corrosion, galvanic corrosion, intergranular corrosion, sensitization
02/06/14 17:06 RHC020 Changes in surface morphology and work function caused by corrosion in aluminum alloys Mingshan Xuea, b, Juan Xiea, Wen Lia, b, Corresponding author contact information, E-mail the corresponding author, Fajun Wanga, Junfei Oua, Chenggang Yanga, Changquan Lia, Zhenchen Zhonga, Zhonghao Jiangb Journal of Physics and Chemistry of Solids Volume 73, Issue 6, June 2012, Pages 781‰ÛÒ787 2012 Corrosion behavior of a material is complicated and can affect strongly its surface physical and chemical properties. In this study, the effect of corrosion on surface morphology and electron work function (EWF) of various Al alloys was comparatively investigated using a scanning electron microscopy and a scanning Kelvin probe. The experimental results showed that the change in EWF with corrosion time was not linear, but firstly increased and then decreased. The theoretical treatments demonstrated that such a change in EWF did not only depend on the surface roughness, but also correlate with oxide layers formed at the surfaces of Al alloys. The present results can also be used to reasonably explain the correlation between surface roughness and EWF reported previously. http://www.sciencedirect.com/science/article/pii/S0022369712000510 A. Alloys; C. Electron microscopy; D. Electronic structure
1/13/2014 15:03:19 SKP Cathodic disbonding of an unpigmented epoxy coating on mild steel under semi- and full-immersion conditions Huichao Bi, John Sykes Corrosion Science 53 (2011) 3416‰ÛÒ3425 2011 Cathodic disbonding of an unpigmented epoxy coating around a defect was studied with samples fully- and semi-immersed in 3.5 wt.% NaCl solution. Disbonding and the growth of blisters were monitored by scanning acoustic microscopy, which showed growth of blisters within the disbond for both type of samples. Scanning Kelvin probe potential maps suggest that blisters first form at local anodes. For semi-immersed samples, disbonding of the immersed part and the non-immersed part propagate with parabolic kinetics at identical rates, similar to fully-immersed samples. This implies that ion transport is along the coating‰ÛÒmetal interface in both cases. http://www.sciencedirect.com/science/article/pii/S0010938X11003398 : organic coatings, mild steel, oxygen reduction, paint coatings
3/29/2014 7:32:17 SKP5050 [6,6]-Phenyl- C61-butyric acid 2-((2-(dimethylamino)ethyl)(methyl)amino)-ethyl Ester as an Acceptor and Cathode Interfacial Materials in Polymer Solar Cells Menglan Lv, Ming Lei, Jin Zhu, Tadahiko Hirai, and Xiwen Chen ACS Appl. Mater. Interfaces, Mar-14 An amine-based alcohol soluble fullerene [6,6]-phenyl-C61-butyric acid 2-((2-(dimethylamino)ethyl)(methyl)amino)-ethyl ester (PCBDAN) with four fold electron mobility of 6,6-phenyl C61-butyric acid methyl ester (PCBM) is applied successfully as an acceptor and cathode interfacial material in polymer solar cells ITO/P3HT:PCBDAN/MoO3/Ag, where ITO alone is used as the cathode and poly(3-hexylthiophene) (P3HT) as a donor. XPS depth profile confirms a favorable vertical phase separation is formed where P3HT is rich on air/active blend interface and PCBDAN is rich at the buried interface with ITO and thus reduces the work function of ITO for use as the cathode. A moderate power conversion efficiency (PCE) of 3.1 % is achieved. The slightly low PCE could be due to un-optimized morphology and low structure ordering of P3HT in the blends. However, this result demonstrates that the amine-based fullerene could be used as the acceptor and cathode interfacial material, which eliminating multilayer device fabrication process. Since PCBDAN has high electron mobility, it would have potential applications in nano-structured organic solar cells. In the near future, alcohol processible high efficient organic/polymer solar cells can be anticipated. http://pubs.acs.org/doi/abs/10.1021/am5007047 : fullerenes, photovoltaic devices, organic electronics, conjugated polymers, solar cells
02/03/15 14:32 KP020 Effect of Polyelectrolyte Electron Collection Layer Counteranion on the Properties of Polymer Solar Cells Thu Trang Do, Hee Seob Hong, Ye Eun Ha, Juyun Park, Yong-Cheol Kang and Joo Hyun Kim ACS Applied Materials and Interfaces, 2015 Jan-15 Polyviologen (PV) derivatives are known materials used for adjusting the work function (WF) of cathodes by reducing the electron injection/collection barrier at the cathode interface. To tune and improve device performance, we introduce different types of counteranions (CAs), such as bromide, tetrafluoroborate, and tetraphenylborate, to a PV derivative. The effective WF of the Al cathode is shown to depend on the size of the CA, indicating that a Schottky barrier can be modulated by the size of the CA. Through the increased size of the CA from bromide to tetraphenylborate, the effective WF of the Al cathode is gradually decreased, indicating a decreased Schottky barrier at the cathode interface. In addition, the change of the power conversion efficiency (PCE) and the short circuit current (Jsc) value show good correlation with the change of the WF of the cathode, signifying the typical transition from a Schottky to an Ohmic contact. The turn-on electric field of the electron-only device without PV was 0.21 MV/cm, which is dramatically higher than those of devices with PV-X (0.07 MV/cm for PV-Br, 0.06 MV/cm for PV-BF4, and 0.05 MV/cm for PV-BPh4) This is also coincident with a decrease in the Schottky barrier at the cathode interface. The device ITO/PEDOT/P3HT:PCBM/PV/Al, with a thin layer of PV derivative and tetraphenylborate CA as the cathode buffer layer, has the highest PCE of 4.02%, an open circuit voltage of 0.64 V, a Jsc of 11.6 mA/cm2, and a fill factor of 53.0%. Our results show that it is possible to improve the performance of polymer solar cells by choosing different types of CAs in PV derivatives without complicated synthesis and to refine the electron injection/collection barrier height at the cathode interface. http://pubs.acs.org/doi/abs/10.1021/am5082606 polyelectrolyte; anion exchange; polymer solar cell; buffer layer
02/06/14 17:04 RHC020 Lightning rod effect in surface work function of semiconductor nanomaterials Mingshan Xue1,a), Wenfeng Wang1, Junfei Ou1, Fajun Wang1 and Wen Li1 Appl. Phys. Lett. 102, 243110 (2013) 2013 The inherent correlation between the work function and surface microstructures of semiconductor nanomaterials (SNMs) was investigated. It was found that the work function of SNMs decreased with the increase of the degree of order of SNMs. The well-aligned SNMs corresponded to the lowest work function, which was just as the lightning rod effect being of advantage to the electron transport in SNMs. Such a simple and intuitive analogy to the change trend of work function is of help to enhance the understanding of electron transport of SNMs. http://scitation.aip.org/content/aip/journal/apl/102/24/10.1063/1.4812238 Nanorods AnnealingII-VI semiconductors Electronic transport Lightning discharges Surface structure Double layers Capacitors Electrostatics Nanowires
11/04/14 14:15 SKP5050 Accelerated degradation of Al3+ doped ZnO thin films using damp heat test Ivan Litzov, Hamed Azimi, Gebhard Matt, Peter Kubis, Tobias Stubhan, Georgi Popov and Christoph J. Brabec Organic Electronics (15:2), 2014, pp. 569-576. Feb-14 Two different types of aluminum-doped zinc oxide (AZO) thin films were fabricated using low cost sol‰ÛÒgel technique. By applying damp heat testing, the optical and electrical properties of those films were investigated under the influence of accelerated degradation from moisture or moisture vapor. Complementary measurements of optical transmittance, work function, and conductivity allowed exploring the degradation of AZO thin films and the corresponding OPV devices. We found that optical properties like transmittance, absorption coefficient, and band gap are not influenced by temperature and moisture. However, an increase in the work function, and a decrease in the conductivity of AZO films were observed upon damp heat exposure indicating the formation of a barrier or depletion layer at the metal oxide semiconductor interface. http://www.sciencedirect.com/science/article/pii/S1566119913005314 *
1/13/2014 15:20:02 * Direct comparison of photoemission spectroscopy and in situ Kelvin probe work function measurements on indium tin oxide films M.M. Beerbom, B. L̤gel, A.J. Cascio, B.V. Doran, R. Schlaf Journal of electron Spectroscopy and Related Phenomena, Volume 152, Issues 1‰ÛÒ2, June 2006, Pages 12‰ÛÒ17 2006 The work function of commercially available indium tin oxide (ITO) films on glass substrates was measured using photoemission spectroscopy (PES) and ultra-high vacuum (UHV) Kelvin probe in direct comparison. Absolute Kelvin probe work function values were determined via calibration of the measured contact potential difference (CPD) using an in situ sputtered Au reference sample. The Kelvin probe data confirmed that ultraviolet photoemission spectroscopy (UPS) measurements change the work function of ITO surfaces previously exposed to ambient environment, when measured without in situ surface cleaning procedures. The results also demonstrate that both Kelvin probe and PES yield virtually identical work function values, as long as the Kelvin probe data are calibrated against a known standard. As a consequence, previously reported higher work function values determined with Kelvin probe as compared to values obtained with UPS on similar samples are likely related to a photochemically generated surface dipole during UPS measurements. Comparison between Kelvin probe and low intensity X-ray photoemission spectroscopy (LIXPS) work function measurements demonstrated that accurate work function measurements on ITO previously exposed to the ambient are possible with PES. http://www.sciencedirect.com/science/article/pii/S0368204806000077 *
1/13/2014 15:11:12 * Adsorption structure of phenylphosphonic acid on an alumina surface Shinjiro Yagyu, Michiko Yoshitake, Nataliya Tsud, Toyohiro Chikyow Applied Surface Science, Volume 256, Issue 4, 30 November 2009, Pages 1140‰ÛÒ1143 2009 The adsorption structure of phenylphosphonic acid (PPOA) on an alumina surface was investigated as a function of exposure and temperature using infrared reflected absorption spectroscopy (IRAS) and a Kelvin probe. The alumina surface was held at room temperature during deposition. At monolayer adsorption, P O and Phenyl-P bands are observed, which indicate the creation of P O Al bonds. The aromatic ring plane is positioned perpendicular to the surface, i.e. deprotonated PPOA stands vertically on the surface. At multilayer adsorption, P O and P OH bands appear in the spectra. The multilayer PPOA film starts to desorb at 400 K. From 400 to 700 K, the IRAS spectra are similar to the monolayer spectrum, indicating that the multilayer structure reverses to the monolayer-like PPOA adlayer by heating. The acid molecules start to desorb at 700 K. http://www.sciencedirect.com/science/article/pii/S0169433209006874 *
1/13/2014 15:12:33 * Adsorptions tructure and work function of dicarboxylic acid on Cu(1 1 0) surface Shinjiro Yagyu, Michiko Yoshitake, Toyohiro Chikyow Applied Surface Science, Volume 254, Issue 23, 30 September 2008, Pages 7835‰ÛÒ7837 2008 We investigated the relation between work function and the adsorption structure of dicarboxylic acids (organic molecules) such as succinic acid (HOOC‰ÛÒCH2‰ÛÒCH2‰ÛÒCOOH) and an adipic acid (HOOC‰ÛÒ(CH2)4‰ÛÒCOOH) on a Cu(1 1 0) surface (electrode) as a function of the surface temperature using a Kelvin probe (KP). The work function changes of the two acids are similar. The work function increases by adsorption at room temperature due to ionization of molecules and then decreases with increasing temperature until 450 K due to the effects of change in the dipole moment of the conformational change of the molecule. From 450 to 600 K, the work function is constant because of competition between desorption and change in the dipole moment of molecules. It then reached the clean-surface value. Experiments clarified that the work function was affected by the adsorbed difference in conformation of molecules. http://www.sciencedirect.com/science/article/pii/S0169433208003693 *
11/04/14 21:06 SKP5050 Interface junction at anatase/rutile in mixed-phase TiO2: Formation and photo-generated charge carriers properties Xiaoru Zhang, Yanhong Lin, Dongqing He, Jianfu Zhang, Zhiyong Fan, Tengfeng Xie Chemical Physics Letters (504:1-3), 2011, pp. 71-75 Feb-11 Nanosized TiO2 photocatalysts of anatase, rutile and mixed-phase were synthesized through hydrolysis method. The influence of the interface junction between anatase and rutile TiO2 on the photo-generated charge carriers properties were studied by Kelvin probe (KP), surface photovoltage (SPV) and transient photovoltage (TPV) techniques. The KP results revealed that the difference of the surface work function between anatase and rutile might cause the formation of built-in field at the interface in mixed-phase TiO2. The role of the interface junction was further testified through the characteristics of photo-generated charge carriers by SPV and TPV. http://www.sciencedirect.com/science/article/pii/S0009261411001011 *
02/06/14 17:24 KP with SPV Surface photovoltage study of photogenerated charges in ZnO nanorods array grown on ITO Qidong Zhao, Dejun WangCorresponding author contact information, E-mail the corresponding author, Linlin Peng, Yanhong Lin, Min Yang, Tengfeng Xie Chemical Physics Letters Volume 434, Issues 1‰ÛÒ3, 26 January 2007, Pages 96‰ÛÒ100 2007 A well-aligned nanorods array of ZnO was chemically grown on conductive ITO substrate at low temperature. The photogenerated charges at surface and interface were examined by surface photovoltage techniques based on both Kelvin probe and lock-in amplifier with dc bias. The photovoltage response bands related to band-to-band transition and bound excitons were discriminated. We demonstrated the spectrum-dependent transfer characteristic of photogenerated charges at the surface of ZnO nanorods array and the interface between ZnO and ITO. http://www.sciencedirect.com/science/article/pii/S0009261406017702 *
1/13/2014 15:10:31 SKP5050 Work function engineering in low-temperature metals Nicholas D. Orf, Iain D. Baikie, Ofer Shapira, and Yoel Fink * 2009 Semiconductor devices require conducting electrodes with disparate work functions for their operation. Of recent interest are fluidic processing approaches for large-area devices, which present unique challenges in the identification of materials having disparate work functions but similar melting temperatures. Such materials may be engineered by alloying with low-melting temperature metals. As a demonstration, the work function of tin and four binary tin alloys is measured by ultraviolet photoemission spectroscopy and Kelvin probe method. We demonstrate the control of metal work function by 600 meV through alloying while keeping the melting temperature within a 140 å¡C range. http://www.rle.mit.edu/pbg/Documents/Work_Function_Engineering_in_Metal_ Alloys_MAR_2009.pdf *
1/23/2015 12:31:27 APS Semiconducting properties of spinel tin nitride and other IV3N4 polymorphs Christopher M. Caskey Christopher M. Caskey Jason A. Seabold Jason A. Seabold Vladan Stevanovi€à Vladan Stevanovi€à Ming Ma Ming Ma Wilson A. Smith Wilson A. Smith David S. Ginley David S. Ginley Nathan R. Neale Nathan R. Neale Ryan M. Richards Ryan M. Richards Stephan Lany Stephan Lany Andriy Zakutayev Andriy Zakutayev J. Mater. Chem. Dec-14 Tin nitride, Sn3N4, is a semiconductor composed of common elements with a band gap in the visible range, making it a candidate for optical and electronic applications. In this work, the semiconducting properties of tin nitride are explored by thin-film experiments and first-principles theory to evaluate the prospects of this material for optoelectronic applications. Calculations of related group IV nitride polymorphs provide additional insight into the properties and challenges associated with this class of semiconductors. Experimentally, in Sn3N4 polycrystalline thin films the electron concentration was found to be 1018 cm‰öÕ3 with Hall mobility of 1 cm2 V‰öÕ1 s‰öÕ1 and a minority carrier (holes) diffusion length of 50‰ÛÒ100 nm. The optical absorption onset was determined at 1.6 eV and an ionization potential was measured at 5.9‰ÛÒ6.0 eV. From theory, a direct band gap of 1.54 eV was determined with weak dipole-forbidden lowest energy transitions and the ionization potential was determined to be 6.5 eV, both in reasonable agreement with the experiments. Calculations also predict an exceptionally small electron effective mass (0.18 m0) and a large hole effective mass (12.9 m0), which may be in part responsible for the short hole diffusion length. To elucidate the origin of the heavy holes in Sn3N4, elemental and crystallographic trends in electronic structure and thermochemical properties are calculated in the IV3N4 polymorphs. It was found that hole effective masses generally increase down the period and are structure-dependent, while electron effective masses decrease down the period and show no strong structural trends. These results suggest that changing composition in the group-IV nitride alloys will have a large impact on the fundamental semiconductor properties such as carrier effective masses, and provide other insight into the materials chemistry of Sn3N4 and the IV3N4 family. http://www.researchgate.net/publication/270005820_Semiconducting_properties_of_spinel_tin_nitride_and_other_IV3N4_polymorphs *
3/13/2015 9:09:25 SKP5050 ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution Aiping Wu, Liqiang Jing, Jianqiang Wang, Yang Qu, Ying Xie, Baojiang Jiang, Chungui Tian & Honggang Fu Scientific reports (2015) Mar-15 The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy ‰ÛÏcontrolling competitive reaction‰Û strategy by selecting the thiourea as S2‰öÕ source and Zn(Ac)2åá2H2O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m2g‰öÕ1, microsphere size of 100 nm and grain size of 3 nm can be obtained. The formation of PCMS is verified by TEM, XAES, XPS, Raman and IR methods. Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE. As a result, the PCMS-1 shows the promising activity up to 367 ë¼mol h‰öÕ1 under Pt-free condition. The PHE activity has no obvious change after addition 1 wt.% Pt, implying the presence of active catalytic sites for hydrogen evolution in the PCMS-1. The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE. http://www.nature.com/srep/2015/150309/srep08858/full/srep08858.html *
11/05/14 11:20 KP020 Surface Passivation and Antireflection Behavior of ALD on n-Type Silicon for Solar Cells Ing-Song Yu, Yu-Wun Wang, Hsyi-En Cheng, Zu-Po Yang and Chun-Tin Lin International Journal of Photoenergy, 2013, ID 431614 2013 Atomic layer deposition, a method of excellent step coverage and conformal deposition, was used to deposit TiO2 thin films for the surface passivation and antireflection coating of silicon solar cells. TiO2 thin films deposited at different temperatures (200å¡C, 300å¡C, 400å¡C, and 500å¡C) on FZ n-type silicon wafers are in the thickness of 66.4‰Ûänm å± 1.1‰Ûänm and in the form of self-limiting growth. For the properties of surface passivation, Si surface is effectively passivated by the 200å¡C deposition TiO2 thin film. Its effective minority carrier lifetime, measured by the photoconductance decay method, is improved 133% at the injection level of ‰Ûäcm‰öÕ3. Depending on different deposition parameters and annealing processes, we can control the crystallinity of TiO2 and find low-temperature TiO2 phase (anatase) better passivation performance than the high-temperature one (rutile), which is consistent with the results of work function measured by Kelvin probe. In addition, TiO2 thin films on polished Si wafer serve as good ARC layers with refractive index between 2.13 and 2.44 at 632.8‰Ûänm. Weighted average reflectance at AM1.5G reduces more than half after the deposition of TiO2. Finally, surface passivation and antireflection properties of TiO2 are stable after the cofire process of conventional crystalline Si solar cells. http://www.hindawi.com/journals/ijp/2013/431614/abs/ *
1/13/2014 15:08:06 SKP5050 Anomalous Tunneling in Carbon/Alkane/TiO2/Gold Molecular Electronic Junctions: Energy Level Alignment at the Metal/Semiconductor Interface Haijun Yan, and Richard L. McCreery ACS Appl. Mater. Interfaces, 2009 2009 Carbon/TiO2/gold electronic junctions show slightly asymmetric electronic behavior, with higher current observed in current density (J)/voltage (V) curves when carbon is biased negative with respect to the gold top contact. When a‰ö¼1-nm-thick alkane film is deposited between the carbon and TiO2, resulting in a carbon/alkane/TiO2/gold junction, the current increases significantly for negative bias and decreases for positive bias, thus creating a much less symmetric J/V response. Similar results were obtained when SiO2 was substituted for the alkane layer, but Al2O3 did not produce the effect. The observation that, by the addition of an insulating material between carbon and TiO2, the junction becomes more conductive is unexpected and counterintuitive. Kelvin probe measurements revealed that while the apparent work function of the pyrolyzed photoresist film electrode is modulated by surface dipoles of different surface-bound molecular layers, the anomalous effect is independent of the direction of the surface dipole. We purpose that by using a nanometer-thick film with a low dielectric constant as an insertion layer, most of the applied potential is dropped across this thin film, thus permitting alignment between the carbon Fermi level and the TiO2 conduction band. Provided that the alkane layer is sufficiently thin, electrons can directly tunnel from carbon to the TiO2 conduction band. Therefore, the electron injection barrier at the carbon/TiO2 interface is effectively reduced by this energy-level alignment, resulting in an increased current when carbon is biased negative. The modulation of injection barriers by a low-ë¼ molecular layer should be generally applicable to a variety of materials used in micro- and nanoelectronic fabrication. http://www.chem.ualberta.ca/~mccreery/RLM%20publication%20PDFs/mccre ery205_anomalous%20tunneling.pdf *
11/04/14 21:18 SKP5050 Optoelectronic Characteristics of Zinc Oxide Nanorods/P3HT Hybrid Junctions Investigated Using Surface Photovoltage Method Dawei Kang, Aimin Liu, Jiming Bian and Yongchang Sang ECS Solid State Lett., (1:1), 2012, pp. 15-17 Jul-12 The hybrid junctions were fabricated on the ITO glass by combining the hydrothermal method grown zinc oxide nanorods (ZnO NRs) with spin coated P3HT (poly-3-hexyl-thiophene) films. Surface photovoltage technique using Kelvin probe and lock-in amplifier was utilized to study the photo-generated charges at surface and interface of as-grown inorganic-organic hybrid junctions. The results illustrated that the SPS (surface photovoltage spectroscopy) response intensity was significantly enhanced and response range was expanded due to the incorporation of P3HT in ZnO NRs/P3HT hybrid junctions. Moreover, it was inferred that the P3HT could reduce the surface photo-generated charges and shorten the relaxation time of recombination process in the ZnO NRs/P3HT structure, which would be favorable for the photovoltaic applications of ZnO NRs/P3HT bulk hybrid junctions. http://ssl.ecsdl.org/content/1/1/P15.short *
11/04/14 22:16 SKP5050 Annealing Effect for SnS thin films prepared by high-vacuum evaporation Naidu Revathi, Sergei Bereznev, Mihkel Loorits, Jaan Raudoja, Julia Lehner, Jelena Gurevits, Rainer Traksmaa, Valdek Mikli, Enn Mellikov and Olga Volobujeva Journal of Vacuum Science and Technology A, (32), 2014, 061506 Sep-14 Thin films of SnS are deposited onto molybdenum-coated soda lime glass substrates using the high-vacuum evaporation technique at a substrate temperature of 300‰Ûäå¡C. The as-deposited SnS layers are then annealed in three different media: (1) H2S, (2) argon, and (3) vacuum, for different periods and temperatures to study the changes in the microstructural properties of the layers and to prepare single-phase SnS photoabsorber films. It is found that annealing the layers in H2S at 400‰Ûäå¡C changes the stoichiometry of the as-deposited SnS films and leads to the formation of a dominant SnS 2 phase. Annealing in an argon atmosphere for 1‰Ûäh, however, causes no deviations in the composition of the SnS films, though the surface morphology of the annealed SnS layers changes significantly as a result of a 2‰Ûäh annealing process. The crystalline structure, surface morphology, and photosensitivity of the as-deposited SnS films improves significantly as the result of annealing in vacuum, and the vacuum-annealed films are found to exhibit promising properties for fabricating complete solar cells based on these single-phase SnS photoabsorber layers. http://scitation.aip.org/content/avs/journal/jvsta/32/6/10.1116/1.4896334 *
4/28/2015 9:21:24 UHVKP020 A new Stark decelerator based surface scattering instrument for studying energy transfer at the gas-surface interface Daniel P. Engelhart, Fabian Gr̤tz, Roman J. V. Wagner, Henrik Haak, Gerard Meijer, Alec M. Wodtke and Tim Sch̤fer Review of Scientific Instruments (86:4), 2015, 043306 2015 We report on the design and characterization of a new apparatus for performing quantum-state resolved surface scattering experiments. The apparatus combines optical state-specific molecule preparation with a compact hexapole and a Stark decelerator to prepare carrier gas-free pulses of quantum-state pure CO molecules with velocities controllable between 33 and 1000 m/s with extremely narrow velocity distributions. The ultrahigh vacuum surface scattering chamber includes homebuilt ion and electron detectors, a closed-cycle helium cooled single crystal sample mount capable of tuning surface temperature between 19 and 1337 K, a Kelvin probe for non-destructive work function measurements, a precision leak valve manifold for targeted adsorbate deposition, an inexpensive quadrupole mass spectrometer modified to perform high resolution temperature programmed desorption experiments and facilities to clean and characterize the surface. http://scitation.aip.org/content/aip/journal/rsi/86/4/10.1063/1.4918797 *
11/05/14 12:19 KP020 Surface states of ZnO nanoparticles effect on the performance of inverted-organic solar cells Wenjing Qin, Xinrui Xu, Dongyue Liu, Chunyu Ma, Liying Yang, Shougen Yin, Fengling Zhang and Jun Wei Journal of Renewable and Sustainable Energy (5), 2013, 053106 Sep-13 ZnO is a promising material used as the electron transport layer in the inverted organic solar cells (IOSCs). However, the electrical or photoelectric properties of ZnO nanoparticles are governed by the surface states of the nanoparticles. Here, we demonstrate that the large number of hydroxyl (-OH) existed on the ZnO nanoparticles films have a vast impact on the performance of IOSCs with the structure of ITO/ZnO/poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C61 butyric acid methyl ester (PCBM)/MoO3/Ag. The surface hydroxyl groups depredate active layer via elevating photocatalytic activity of the ZnO, hence deteriorate the device performance. Experimental results show that hydroxyl groups can be effectively detached from ZnO film by annealing. Hydroxyl groups detach more with increasing annealing temperature, resulting in less degradation of the active layer. Therefore, the efficiency is significantly improved due to increased photo-current density and decreased series resistance of IOSCs. The best device exhibits a power conversion efficiency of 3.05% after annealing at 150‰Ûäå¡C. http://scitation.aip.org/content/aip/journal/jrse/5/5/10.1063/1.4821219 *
11/10/14 09:15 SKP5050 Understanding the bond-energy, hardness, and adhesive force from the phase diagram via the electron work function Hao Lu, Xiao chen Huang and Dongyang Li Journal of Applied Physics (116), 2014, 173506 2014 Properties of metallic materials are intrinsically determined by their electron behavior. However, relevant theoretical treatment involving quantum mechanics is complicated and difficult to be applied in materials design. Electron work function (EWF) has been demonstrated to be a simple but fundamental parameter which well correlates properties of materials with their electron behavior and could thus be used to predict material properties from the aspect of electron activities in a relatively easy manner. In this article, we propose a method to extract the electron work functions of binary solid solutions or alloys from their phase diagrams and use this simple approach to predict their mechanical strength and surface properties, such as adhesion. Two alloys, Fe-Ni and Cu-Zn, are used as samples for the study. EWFs extracted from phase diagrams show same trends as experimentally observed ones, based on which hardness and surface adhesive force of the alloys are predicted. This new methodology provides an alternative approach to predict material properties based on the work function, which is extractable from the phase diagram. This work may also help maximize the power of phase diagram for materials design and development. http://scitation.aip.org/content/aip/journal/jap/116/17/10.1063/1.4901070 *
7/27/2015 11:35:46 APS02 Copper thiocyanate: An attractive hole transport/extraction layer for use in organic photovoltaic cells Neil D. Treat, Nir Yaacobi-Gross, Hendrik Faber, Ajay K. Perumal, Donal D. C. Bradley, Natalie Stingelin and Thomas D. Anthopoulos Appl. Phys. Lett. 107, 013301 (2015) 2015 We report the advantageous properties of the inorganic molecular semiconductor copper(I) thiocyanate (CuSCN) for use as a hole collection/transport layer (HTL) in organic photovoltaic (OPV) cells. CuSCN possesses desirable HTL energy levels [i.e., valence band at ‰öÕ5.35‰ÛäeV, 0.35‰ÛäeV deeper than poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS)], which produces a 17% increase in power conversion efficiency (PCE) relative to PEDOT:PSS-based devices. In addition, a two-fold increase in shunt resistance for the solar cells measured in dark conditions is achieved. Ultimately, CuSCN enables polymer:fullerene based OPV cells to achieve PCE‰Ûä>‰Ûä8%. CuSCN continues to offer promise as a chemically stable and straightforward replacement for the commonly used PEDOT:PSS. http://scitation.aip.org/content/aip/journal/apl/107/1/10.1063/1.4926408 *
6/24/2015 15:40:41 APS02 Efficient organic solar cells using copper(I) iodide (CuI) hole transport layers Ying Peng, Nir Yaacobi-Gross, Ajay K. Perumal, Hendrik A. Faber, George Vourlias, Panos A. Patsalas, Donal D. C. Bradley, Zhiqun He and Thomas D. Anthopoulos Appl. Phys. Lett. 106, 243302 (2015) 2015 We report the fabrication of high power conversion efficiency (PCE) polymer/fullerene bulk heterojunction (BHJ) photovoltaic cells using solution-processed Copper (I) Iodide (CuI) as hole transport layer (HTL). Our devices exhibit a PCE value of ‰ö¼5.5% which is equivalent to that obtained for control devices based on the commonly used conductive polymer poly(3,4-ethylenedioxythiophene): polystyrenesulfonate as HTL. Inverted cells with PCE‰Ûä>3% were also demonstrated using solution-processed metal oxide electron transport layers, with a CuI HTL evaporated on top of the BHJ. The high optical transparency and suitable energetics of CuI make it attractive for application in a range of inexpensive large-area optoelectronic devices. http://scitation.aip.org/content/aip/journal/apl/106/24/10.1063/1.4922758 *
6/24/2015 15:33:40 SKP5050 Efficient organic solar cells using copper(I) iodide (CuI) hole transport layers Ying Peng, Nir Yaacobi-Gross, Ajay K. Perumal, Hendrik A. Faber, George Vourlias, Panos A. Patsalas, Donal D. C. Bradley, Zhiqun He and Thomas D. Anthopoulos Appl. Phys. Lett. 106, 243302 (2015) 2015 We report the fabrication of high power conversion efficiency (PCE) polymer/fullerene bulk heterojunction (BHJ) photovoltaic cells using solution-processed Copper (I) Iodide (CuI) as hole transport layer (HTL). Our devices exhibit a PCE value of ‰ö¼5.5% which is equivalent to that obtained for control devices based on the commonly used conductive polymer poly(3,4-ethylenedioxythiophene): polystyrenesulfonate as HTL. Inverted cells with PCE‰Ûä>3% were also demonstrated using solution-processed metal oxide electron transport layers, with a CuI HTL evaporated on top of the BHJ. The high optical transparency and suitable energetics of CuI make it attractive for application in a range of inexpensive large-area optoelectronic devices. http://scitation.aip.org/content/aip/journal/apl/106/24/10.1063/1.4922758 *
1/13/2014 14:44:28 SKP5050 with SPV Large surface photovoltages observed at methyl-terminated silicon surfaces synthesised through a two-step chlorination-alkylation method Named: Nicholas Alderman,* ab Lefteris Danos,a Martin C. Grosselb and Tom Markvart * 2012 Methylation of the silicon surface through a chlorinationalkylation method has been used to improve the electronic properties of silicon. Upon alkylation of the surface, an increase in the minority carrier recombination lifetime and the surface photovoltage is observed, in line with an increase in surface charge. A likely explanation of this unusually large band bending is charge accumulation during the removal of chlorine from the surface http://pubs.rsc.org/en/content/pdf/article/2012/ra/c2ra20465g *
08/04/15 14:05 KP020 Two-steps strategy to clarify the roles of solution processed PFN interfacial layer in high efficient polymer solar cells Qianqian Sun, Fujun Zhang, Jian Wang, Qiaoshi An, Chen Zhao, LingLiang Li, Feng Teng and Bin Hu Journal of Materials Chemistry A, 2015 2015 Solution Processed PFN interfacial layer has been demonstrated as an efficient method to improve the performance of polymer solar cells (PSCs). The champion power conversion efficiency (PCE) of PSCs with PBT7-Th:PC71BM as the active layer was increased from 6.13% to 7.72% by directly spin-coating PFN methanol solution on the surface of active layers or to 8.50% for the active layer with 4 min PFN methanol solution soaking. The champion PCE of PSCs was further increased to 8.69% for the active layers with a two-steps treatment, 4 min methanol soaking and then directly spin-coating PFN methanol solution. A 12.6% PCE improvement was obtained by using the two-steps strategy compared with directly spin-coating PFN methanol solution on the active layers. The methanol soaking active layers plays the key role in forming the more ideal vertical phase separation for efficient exciton dissociation, charge carrier transport and collection. An ultrathin PFN interfacial dipole layer can be obtained by directly spin-coating PFN methanol solution. The two-steps strategy may provide a simple and effective method to finely optimize the phase separation and obtain an ultrathin PFN interfacial dipole layer for the performance improvement of PSCs. http://pubs.rsc.org/en/content/articlelanding/2015/ta/c5ta05117g#!divAbstract *
7/27/2015 11:06:35 SKP5050 Direct Evidence on the Efficient Hole-Collecting Process of CoOx Cocatalyst for Photocatalytic Reaction: A Surface Photovoltage Study Shuo Li, Libo Hou, Lijing Zhang, Liping Chen, Yanhong Lin, Dejun Wang and Tengfeng Xie Journal of Materials Chemistry A, 2015 2015 The authentic effect of a cocatalyst in photocatalytic reaction is one of the major to issues in photocatalysis research. Herein, the efficient hole-collecting role of CoOx cocatalyst grown on TiO2-nanotubes has been directly proved by surface photovoltage (SPV) spectroscopy. Transient SPV measurement provides evidence for the CoOx cocatalyst that could significantly prolong the life-time of photogenerated holes. Furthermore, it is proposed the hole-collecting effect can be attributed to the work function difference between TiO2 and CoOx interface. These findings demonstrates that the development of cocatalyst with suitable work function can be a general strategy for photoconversion applications. http://pubs.rsc.org/en/content/articlelanding/2015/ta/c5ta04653j#!divAbstract *
7/28/2015 10:16:01 SKP5050 Dual Ternary System for Highly Efficient ITO-free Inverted Polymer Solar Cells Zuosheng Peng, Yuxin Xia, Feng Gao, Kang Xiong, Zhanhao Hu, David James, Junwu Chen, Ergang Wang and Lintao Hou Journal of Materials Chemistry A, 2015 2015 In this study, it has been found that a very fine nanostructure can be realized by mixing 1-chloronaphthalene (CN) ‰ÛÒ a high-boiling solvent into a binary chorobenezene (CB): 1,8 - diiodooctane (DIO) solvent mixture to form a ternary solvent system. An improvement in energy level alignment is also obtained by doping ICBA into a binary PTB7:PCBM[70] blend, whereby the ternary solute system provides an extra new pathway for charge transfer from PTB7 to the PCBM[70]:ICBA alloy. This is confirmed by imaging the surface morphology of the active layer using AFM, monitoring the transient film formation process and measuring charge transfer states with Fourier transform photocurrent spectroscopy. An encouraging PCE of 7.65 % is achieved from the dual ternary system, which is the highest value ever reported for an ITO-free inverted polymer solar cell with a PEDOT:PSS layer as the top semitransparent electrode ‰ÛÒ a system which is compatible with low-cost large-area roll-to-roll manufacturing. http://pubs.rsc.org/en/content/articlelanding/2015/ta/c5ta03831f#!divAbstract *
6/29/2015 9: 39:41 SKP5050 Highly crystalline, small size, monodisperse ë±-NiS nanocrystal ink as an efficient counter electrode for dye-sensitized solar cells Xiuwen Wang, Bateer Buhe, Ying Xie, Kai Pan, Yongping Liao, Chun-Mei Lv, mingxia li, Siyu Sui and honggang Fu Journal of Materials Chemistry A, 2015 2015 We report the synthesis of highly crystalline, small size, ë±-NiS nanocrystal inks for the fabrication of counter electrode of dye-sensitized solar cells. The monodisperse ë±-NiS nanocrystals (about 7 nm) are obtained via a noninjection, solution-phase chemical synthesis method. During the growth process of ë±-NiS nanocrystals, the Ni‰ÛÒoleate complex, which is generated in situ from the reaction of nickel chloride and sodium oleate, is decomposed and acts effectively as a growth source in synthesizing monodisperse nanocrystals. By controlling the reaction temperature, the resultant nanocrystal sizes and crytallinity can be well tuned. Compared to conventional obtained NiS bulks, the monodisperse ë±-NiS nanocrystals possess an abundance of reaction catalytic sites for dye-sensitized solar cells due to the small particle size and high crystallinity. The first-principles calculations have been first employed to investigate the adsorption energy of I3- molecule on (111) surface of ë±-NiS with equilibrium shape. The DSSCs based on monodisperse ë±-NiS nanocrystal ink with higher crystallinity display the power conversion efficiency of 7.33 %, which is comparable to that based on Pt cathode (7.53 %), but significantly higher than that based on the bulk NiS (4.64 %) and lower crystallinity ë±-NiS nanocrystals (6.32 %). It can be attributed to more reaction catalytic sites due to the surface effect of small ë±-NiS nanocrystals, and the highest work function level (5.5 eV) that matched the redox shuttle potential. We believe that our method paves a promising way to design and synthesize advanced counter electrode materials for energy harvesting. http://pubs.rsc.org/en/content/articlelanding/2015/ta/c5ta02946e#!divAbstract *
4/21/2015 10:06:15 KP020 Extremely thin and robust interconnecting layer providing 76% Fill Factor in a tandem polymer solar cell architecture Alberto Mart Ì­nez-Otero, Quan Liu, Paola Mantilla-Perez, Miguel Montes and Jordi Martorell   Journal of Materials Chemistry A (2015) 2015 In order to allow direct competition against inorganic photovoltaic technologies several years ago the tandem approach was introduced into polymer photovoltaics. Staking two or even more organic solar cells using interconnecting layers (ICL) allows one to overcome intrinsic limitations of conjugated organic molecules, like the quite poor charge carrier mobility. This ICL plays an important role as should function as a charge recombination layer, being optical transparent and should have robustness to protect the bottom subcell. Most tandem works reported so far employed as part of their interlayers thick layers of the acidic PEDOT and/or metallic oxide nanoparticles that need post processing annealings that can be detrimental for the bottom subcell. Here we report a tandem solar cell with identical subcells, in order to overcome the active layer thickness limitation imposed by the relatively low charge mobility that shows a Fill Factor (FF) value never reported for tandem polymer solar cells. Such subcells are series connected by a very thin and strong ICL formed by three layer architecture of MoO3/Ag/PFN. The thickness of this ICL is bellow 20nm and its robustness was confirmed in all the devices fabricated with this and other subcell configurations. There is no need of thermal or solvent annealing in the processing of this ICL. We demonstrate that FFs larger than the ones found in the single junction cells can be reached. A FF as high as 76% was obtained for a tandem solar cell consisting of two identical subcells connected in series. In such configuration, where there is an increase of the total equivalent active layer thickness, the use of the MoO3/Ag/PFN ICL lead to a better performance tandem solar cell by overcoming low charge mobility problems and by improving the FF. The outstanding properties of this charge recombination layer together with newly design polymers will allow for tandem solar cells with efficiencies exceeding the 15% barrier. http://pubs.rsc.org/en/content/articlelanding/2015/ta/c5ta02205c#!divAbstract *
6/30/2015 10:05:49 KP020 Interfacial Modification for improving Inverted Organic Solar Cells by Poly (N-vinylpyrrolidone) Xuan Yu, Xiaoming Yu, Jianjun Zhang, Dekun Zhang, Hongkun Cai and Ying Zhao RSC Advances, 2015 2015 The effect of the thickness of Poly (N-vinylpyrrolidone) interface modifier on the photovoltaic performance of inverted organic solar cells was investigated. Superior interface properties provided efficient charge transport and decreased the charge recombination due to PVP interlayer reduced the energy barrier for electron extraction by lowering the hydroxide radical amount. We obtain an enhanced efficiency of 4.55% (for P3HT:PCBM device) and 6.18% (for PTB7: PC71BM device). http://pubs.rsc.org/en/content/articlelanding/2015/ra/c5ra09427e#!divAbstract *
7/27/2015 11:53:12 KP020 Enhancement of light emission in GaAs epilayers with graphene quantum dots T. N. Lin, K. H. Chih, M. C. Cheng, C. T. Yuan, C. L. Hsu, J. L. Shen, J. L. Hou, C. H. Wu, W. C. Choud and T. Y. Lin RSC Advances Issue 75, 2015 2015 A green and one-step synthesis of graphene quantum dots (GQDs) has been implemented using pulsed laser ablation from aqueous graphene. The synthesized GQDs are able to enhance the photoluminescence (PL) of GaAs epilayers after depositing them on the GaAs surface. An enhancement of PL intensity of a factor of 2.8 has been reached at a GQD concentration of 1.12 mg ml‰öÕ1. On the basis of the PL dynamics, the PL enhancement in GaAs is interpreted by the carrier transfer from GQDs to GaAs due to the work function difference between them. http://pubs.rsc.org/en/content/articlelanding/2015/ra/c5ra09315e#!divAbstract *
7/28/2015 10:30:03 KP020 Spectral weight shift in the valence band density of states and concurrent increase in field emission by hydrogenation of FeCo‰ÛÒSiO2 nanocomposites Debalaya Sarker, S. Ghosh and P. Srivastava RSC Advances 78 (5), 2015, 63377-63381 2015 Hydrogenated and roughened surfaces of hydrogen plasma treated (HPT) FeCo‰ÛÒSiO2 nanogranular films are found to be efficient field emitters in comparison to their as-grown and furnace annealed counterparts. Partial etching using hydrogen plasma roughens the surface and improves the field emission by enhancing the local electric field at the protrusion tips. A layer of Feë«+‰ÛÒH뫉öÕ dipoles over the roughened HPT film surface and enhanced defects are likely to make the composite surface more emission-active by reducing the overall work function. The reconstruction of the electronic structure is mainly attributed to the Fe2+ to Fe3+ conversion and the appearance of anti-bonding states. Further, hydrogen-induced volume expansion of FeCo particles improves the conductivity. Thus tunnelling of electrons from the valence band becomes easier via these inter-gap anti-bonding states. The agglomeration of nanoparticles, out-diffusion of hydrogen, and further etching of the film at a higher substrate temperature of the plasma treated films reduces the FE current density drastically. http://pubs.rsc.org/en/content/articlelanding/2015/ra/c5ra06106g#!divAbstract *
02/10/15 10:11 SKP5050 The Thin Carbon Layer Coated Ti3+-TiO2 Nanocrystalline for Visible-Light Drived Photocatalysis Baojiang Jiang, Yunqi tang, Yang Qu, Jian-Qiang Wang, Ying Xie, Chungui Tian, Wei Zhou and Honggang Fu   Nanoscale, 2015 2015 The black TiO2 with Ti3+ structure attracts enormous attention due to its excellent visible-light drived photocatalytic activity. Herein, an in-situ thermal decomposition approach to synthesize uniform thin carbon coated Ti3+-TiO2 nanocrystal is presented. During the oleic acid-assisted solvothermal process, the crystal size and morphology of TiO2 was controlled through oleic acid with carboxylic acid group. Then the residual small quantities of oleic acid anchored TiO2 was selected as carbon source, which could be in-situ pyrolyzed into carbon layer on TiO2 under high temperature and inert atmosphere. Meanwhile, Ti4+ was partly reduced into Ti3+/oxygen vacancy on the surface of TiO2 due to the carbothermal reduction reaction for carbon-encapsulated Ti3+-TiO2 structure. A series of characterizations indicated that 20nm ~25nm TiO2 nanocrystals obtained were wrapped evenly by 1~2 nm carbon layers, which played an important role for the energy band structure change of TiO2. The presence of carbon layer also improves the Ti3+ stability and the conduction property of composites. The Ti3+/oxygen vacancy created on the surface of TiO2, which was responsible for the remarkable photogenerated charges separation and extended visible-light absorption range. Furthermore, Ti3+/oxygen vacancy and carbon layer could enhance the adsorption ability of O2 so as to promote the photogenerated electrons captured by the adsorbed O2, leading to the great increase in the charge separation. As a result, the composites exhibit high photocatalytic performance for organic pollutants under visible light irradiation. The simple and new method may pave the way to practical application for efficient photocatalytic degradation under visible light. http://pubs.rsc.org/en/content/articlelanding/2015/nr/c5nr00032g#!divAbstract *
11/04/14 21:30 SKP5050 Plasma treatment of ITO cathode to fabricate free electron selective layer in inverted polymer solar cells Chunmei Zhang, Lei Qi, Qiang Chen, Longfeng Lv, Yu Ning, Yufeng Hu,Yanbing Hou and Feng Teng Journal of Materials Chemistry C (41:2), 2014, pp. 8715-8722 Sep-14 With Ar plasma treatment of the indium tin oxide (ITO) cathode, we achieve efficient inverted bulk heterojunction solar cells based on poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester, which do not require electron selective layer. The plasma treatment improves the power conversion efficiency of the device from 1.07% to 3.57% with a fill factor of 66%, open-circuit voltage of 0.60 V, and short-circuit current of 9.03 mA cm‰öÕ2. This result is comparable to the regular inverted devices with an additional electron selective layer. The Kelvin probe detects a reduction in the ITO work function of [similar]0.45 eV after plasma treatment, which finally leads to an increase in the built-in potential and faster carrier extraction. As a result, good device performance is achieved. Because the electron selective layer becomes unnecessary, our strategy suggests a simple way to achieve efficient inverted organic solar cells. http://pubs.rsc.org/en/content/articlelanding/2014/tc/c4tc01777c#!divAbstract *
11/05/14 15:53 SKP5050 + SPS040 Temperature dependence of hole conductor free formamidinium lead iodide perovskite based solar cells Sigalit Aharon, Alexander Dymshits, Amit Rotem and Lioz Etgar Journal of Materials Chemistry A, 2014 Oct-14 Organometal halide perovskite is a promising material in photovoltaic (PV) cells. Within a short time, its performance has increased dramatically to become a real competitor to silicon solar cells. Here we report on the temperature dependence (annealing temperature and the dependence of the photovoltaic parameters on temperature) of formamidinium (FA) lead iodide (FAPbI3), methylammonium (MA) lead iodide (MAPbI3) and their mixture (MAPbI3 : FAPbI3) in hole conductor free perovskite solar cells. These three types of perovskites function both as light harvesters and as hole conductors. Surface photovoltage and optical characterization reveal the p-type behavior and the band gap of the different perovskites. We observed that the ratio between the MA and FA cations might change during the annealing process, affecting the band gap and the stability of the layers. The PV parameters at different temperatures show better stability for the pure MAPbI3 and FAPbI3 solar cells compared to their mixture. Using intensity modulated photovoltage/photocurrent spectroscopy, we found that the diffusion length is weakly dependent on the light intensity, while the charge collection efficiency drops with light intensity for the FAPbI3-based cells. However, for MAPbI3 and the mixture, the charge collection efficiency remains constant for a wide range of light intensities. http://pubs.rsc.org/en/content/articlelanding/2014/ta/c4ta05149a#!divAbstract *
11/05/14 10:57 SKP5050 A solution-processed barium hydroxide modified aluminum doped zinc oxide layer for highly efficient inverted organic solar cells Hong Zhang, Tobias Stubhan, Ning Li, Mathieu Turbiez, Gebhard J. Matt, Tayebeh Ameria and Christoph J. Brabec Journal of Materials Chemistry A (2:44), 2014, pp. 18917-18923 Sep-14 Inverted organic solar cells (iOSCs) with air stable interface materials and top electrodes and an efficiency of 6.01% are achieved by inserting a barium hydroxide (Ba(OH)2) layer between the aluminum doped zinc oxide (AZO) electron extraction layer and the active layer. A low bandgap diketopyrrolopyrrole‰ÛÒquinquethiophene alternating copolymer (pDPP5T-2) and phenyl-C61-butyric acid methyl ester (PC61BM) were chosen as the active layer compounds. Compared to the control device without Ba(OH)2, insertion of a few nm thick Ba(OH)2 layer results in an enhanced VOC of 10%, JSC of 28%, FF of 28% and PCE of 80%. Modification of AZO with a solution processed low-cost Ba(OH)2 layer increased the efficiency of the inverted device by dominantly reducing the energy barrier for electron extraction from PC61BM, and consequently, reduced charge recombination is observed. The drastic improvement in device efficiency and the simplicity of fabrication by solution processing suggest Ba(OH)2 as a promising and practical route to reduce interface induced recombination losses at the cathode of organic solar cells. http://pubs.rsc.org/en/content/articlelanding/2014/ta/c4ta03421j#!divAbstract *
11/05/14 11:54 KP020 Light-induced reversible modification of the work function of a new perfluorinated biphenyl azobenzene chemisorbed on Au (111) Appan Merari Masillamani, Silvio Osella, Andrea Liscio, Oliver Fenwick, Federica Reinders, Marcel Mayor, Vincenzo Palermo, JÌ©rÌ«me Cornil and Paolo SamorÌ Nanoscale (6 :15), 2014, pp. 8969-8977 Jun-14 We describe the synthesis of a novel biphenyl azobenzene derivative exhibiting: (i) a protected thiol anchoring group in the ë±-position to readily form self-assembled monolayers (SAMs) on Au surfaces; and (ii) a terminal perfluorinated benzene ring in the ìä-position to modify the surface properties. The design of this molecule ensured both an efficient in situ photoswitching between the trans and cis isomers when chemisorbed on Au(111), due to the presence of a biphenyl bridge between the thiol protected anchoring group and the azo dye, and a significant variation of the work function of the SAM in the two isomeric states, induced by the perfluorinated phenyl head group. By exploiting the light responsive nature of the chemisorbed molecules, it is possible to dynamically modify in situ the work function of the SAM-covered electrode, as demonstrated both experimentally and by quantum-chemical calculations, revealing changes in work function up to 220 meV. These findings are relevant for tuning the work function of metallic electrodes, and hence to dynamically modulate charge injection at metal‰ÛÒsemiconductor interfaces for organic opto-electronic applications. http://pubs.rsc.org/en/content/articlelanding/2014/nr/c4nr01880j#!divAbstract *
11/05/14 12:08 KP020 BixLa1‰öÕxV O4 solid solutions: tuning of electronic properties via stoichiometry modifications Przemysâa w Kwolek, Kacper Pilarczyk, Tomasz Tokarski, Kornelia Lewandowska and Konrad Szaciâowski Nanoscale (6 :4), 2014, pp. 2244-2254 2014 BixLa1‰öÕxV O4 solid solutions were obtained in the form of fine powder via a microwave-assisted hydrothermal route. The presence of a solid solution in the studied system was confirmed using X-ray diffraction (XRD) and optical spectroscopy techniques. Pure BiVO4 and LaVO4 were obtained in the monoclinic form, whereas solid solutions in the tetragonal, zircon-type structure. The optical band gap dependence on the composition of the solid solution is parabolic, thus there is a possibility to tune this parameter in a wide concentration range, from 2.4 to 4.0 eV. An absorption coefficient maximum is also concentration-dependent, possibly, due to the structural disorder of the samples. Solid solutions with Bi3+ concentration between 11.94 and 32.57 at.% exhibit intense, green luminescence. This indicates the presence of Bi-originated electronic states within the band gap. The value of the conduction band edge potential, measured by both electrochemical impedance spectroscopy and work function measurements, is concentration-independent. Moreover, solid solutions exhibit a photoelectrochemical photocurrent switching effect, thus they may be promising materials for molecular electronics and as dioxygen activators. http://pubs.rsc.org/en/content/articlelanding/2014/nr/c3nr05871a#!divAbstract *
11/04/14 21:24 SKP5050 Charge transfer from cobaltammine complex cations to metal fluoride anions in molecular solids with novel photoelectronic effects (metal: zirconium, titanium) Yu Du, Jihong Yu, Xueming Hong, Xuejin Li and Xiaoqing Tian Dalton Transactions (43), 2014, pp. 14039-14044 Jul-14 [Co(en)3](Ti 2F11) containing H-bonded assembly of a discrete cobaltammine complex cation and titanium fluoride anion was successfully synthesized under solvothermal conditions. A novel photoelectronic effect was observed in the near-UV region. By extending our understanding of this compound, taking into account our previously reported three cobalt complex-containing zirconium fluorides, the mechanism of photoelectronic effects from these molecular solids was determined by investigating the relative work function for their component species with the help of a Scanning Kelvin probe. The results suggest that the charge transfer from the excited cobaltammine complex cations to the metal fluoride anions as a result of the cooperative behaviors might occur upon illumination, which is responsible for these novel photoelectronic effects. http://pubs.rsc.org/en/content/articlelanding/2014/dt/c4dt01543f#!divAbstract *
11/05/14 09:58 SKP5050 Tuning zinc oxide/organic energy level alignment using mixed triethoxysilane monolayers Thomas M. B renner, Gang Chen, Erich P. Meinig, Darick J. Baker, Dana C. Olson, Reuben T. Collins and Thomas E. Furtak Journal of Materials Chemistry (1:37), 2013, pp.5935-5943 Jul-13 Interfacial Energy level alignment influences several critical organic optoelectronic device characteristics including charge transfer barriers, turn-on voltage, and open circuit voltage (Voc). Introduction of dipolar molecular monolayers on metal oxide surfaces has allowed improvements in device performance as well as fundamental studies of energy level alignment in these devices. We demonstrate that dipolar mixed monolayers can be covalently bonded to zinc oxide (ZnO) through the triethoxysilane chemical attachment scheme, and that these monolayers tune the work function of the ZnO surface over 0.6 eV. We then employ mixed monolayer-treated ZnO surfaces as the electron-selective contact in inverted bulk heterojunction photovoltaic devices to determine the correlation between the Voc and the work function of the contact. We find the relationship of ‰öÕ0.14 V eV‰öÕ1 between the Voc and contact work function is consistent with current results and theories of contact influence on Voc. http://pubs.rsc.org/en/content/articlelanding/2013/tc/c3tc30881b#!divAbstract *
11/04/14 22:19 SKP5050 Air-stable in verted structure of hybrid solar cells using a cesium-doped ZnO electron transport layer prepared by a sol‰ÛÒgel process Seungchul Kwon, Kyung-Geun Lim, Myungsun Shim, Hong Chul Moon, Jicheol Park, Gumhye Jeon, Jihyun Shin, Kilwon Cho, Tae-Woo Lee and Jin Kon Kim Journal of Materials Chemistry A (38:1), 2013, pp. 11802-11808 Aug-13 We have developed an air-stable inverted structure of poly(3-hexylthiophene) (P3HT) : cadmium selenide (CdSe) hybrid solar cells using a cesium-doped ZnO (ZnO:Cs) electron transport layer. The ZnO:Cs layer was simply prepared at low temperature by the sol‰ÛÒgel process using a ZnO solution containing cesium carbonate (Cs2CO3). With increasing Cs-doping concentration, the conduction band edge of ZnO is decreased, as confirmed by scanning Kelvin probe microscopy. The energy level of ZnO:Cs is effective for electron transport from CdSe. Consequently, the power conversion efficiency (PCE) of the inverted P3HT : CdSe hybrid solar cells using the ZnO:Cs electron transport layer is 1.14%, which is significantly improved over that (0.43%) of another device without Cs. X-ray photoelectron spectroscopy analysis revealed that the amount of CdSe on the substrate (or the bottom surface) is larger compared with the air (or top) surface regardless of the P3HT : CdSe weight ratio. The vertically inhomogeneous distribution of CdSe in the hybrid solar cells gives better charge transport from CdSe to ZnO:Cs in the inverted structure of the device compared with that in the normal structure. As a result, the inverted hybrid solar cell consisting of 1 : 4 (wt/wt) P3HT : CdSe shows the best efficiency, while the best efficiency of a normal hybrid solar cell is achieved at 1 : 9 (wt/wt) P3HT : CdSe. http://pubs.rsc.org/en/content/articlelanding/2013/ta/c3ta12425h#!divAbstract *
11/05/14 10:42 SKP5050 A combination of Al-doped ZnO and a conjugated polyelectrolyte interlayer for small molecule solution-processed solar cells with an inverted structure Jie Min, Hon g Zhang, Tobias Stubhan, Yuriy N. Luponosov, Mario Kraft, Sergei A. Ponomarenko, Tayebeh Ameri, Ullrich Scherf and Christoph J. Brabec Journal of Materials Chemistry A (1:37), 2013, pp.11306-11311 Jul-13 We successfully demonstrate a smart strategy to use aluminum doped ZnO (AZO) and the thiophene-based conjugated polyelectrolyte P3TMAHT as an interfacial layer in small molecule solution-processed inverted solar cells. Modification of AZO with a thin P3TMAHT layer increases the photovoltaic properties of the inverted cell as a result of reduction in the work function of the cathode with well aligned frontier orbital energy levels for efficient charge transport and reduced surface recombination. The inverted device achieved [similar]16% performance improvement dominantly by recapturing part of the Voc losses when going from conventional to the inverted architecture. In addition, the inverted device using the AZO/P3TMAHT interlayer shows improved device stability in air compared to conventional devices. http://pubs.rsc.org/EN/content/articlelanding/2013/ta/c3ta12162c#!divAbstract *
11/04/14 22:12 SKP5050 Photo-induced synthesis of polypyrrole-silver nanocomposite films on N-(3-trimethoxysilylpropyl)pyrrole-modified biaxially oriented polyethylene terephthalate flexible substrates Ajay Singh, Z akaria Salmi, Nirav Joshi, Purushottam Jha, Ashwini Kumar, HÌ©l̬ne Lecoq, Stephanie Lau, Mohamed M. Chehimi, Dinesh K. Aswal and Shiv K. Gupta RSC Advances (16:3), 2013, pp. 5506-5523 Jan-13 Polypyrrole- silver (PPy‰ÛÒAg) nanocomposite films were prepared on a N-(3-trimethoxysilylpropyl)pyrrole modified biaxially oriented polyethylene terephthalate (BOPET) substrate by photopolymerisation of pyrrole using AgNO3 as a photo-initiator. The films were prepared for a fixed molar concentration of pyrrole (0.5 M), varying molar concentrations of AgNO3 (0.05‰ÛÒ0.7 M) and different UV exposure times (15 min‰ÛÒ180 min). With increasing AgNO3 concentration or with increasing polymerisation time, the film morphology shows a transition from two dimensional lamellar to granular structures. The films are adherent, flexible and exhibit a maximum room temperature electrical conductivity of [similar]15 S cm‰öÕ1 (for AgNO3 [similar] 0.5 M, 120 min of UV exposure). However, the films directly prepared on pristine BOPET show granular morphology and their conductivity value is [similar]0.5 S cm‰öÕ1. The high conductivity of PPy‰ÛÒAg films is attributed to the high conjugation length, the incorporation of Ag nano-particles between the polypyrrole chains and the ordered structure due to the templating effect of the silanised pyrrole layer, as confirmed by GIXRD, FTIR, Raman and temperature dependent conductivity measurements. The metallic state of the embedded Ag nano-particles in the polypyrrole matrix is confirmed by XRD and XPS. The films with the least amount of Ag (AgNO3 [similar] 0.1 M) only show a reversible conductivity change in the opposite manner on exposure to ppm levels of H2S and NH3 gases. The mechanism has been proposed to explain these antagonistic responses for reducing gases. http://pubs.rsc.org/en/content/articlelanding/2013/ra/c3ra22981e#!divAbstract *
11/05/14 09:48 SKP5050 Hydrophilic poly(triphenylamines) with phosphonate groups on the side chains: synthesis and photovoltaic applications Xiaofeng Xu, Yongxiang Zhu, Lianjie Zhang, Jiangman Sun, Jun Huang, Junwu Chen and Yong Cao Journal of Materials Chemistry (22:10), 2012, pp.4329-4336 Jan-12 Two triphen ylamine-based homopolymers PTPA-EP and PTPA-PO3Na2, comprising diethyl phosphonate and sodium phosphonate end groups on side chains, respectively, were synthesized. The UV-vis absorption and photoluminescence (PL) properties of the PTPA-EP and PTPA-PO3Na2 are mainly determined by the conjugated poly(triphenylamine) main chain. The PTPA-EP and PTPA-PO3Na2 possess comparable HOMO levels of around ‰öÕ5.03 eV. The PTPA-EP, with better solubility than PTPA-PO3Na2 in hydrophilic solvents, was utilized as cathode interlayer to construct efficient bulk-heterojunction photovoltaic cells with a low bandgap poly(2,7-carbazole) (PCDTBT) as the polymer donor and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) as the acceptor. The work function of ITO was shifted to ‰öÕ4.3 eV by PTPA-EP, which matches well with the LUMO level of PC71BM for good electron extraction. Inverted solar cells with a device configuration of ITO/PTPA-EP/active layer/MoO3/Al exhibited a power conversion efficiency (PCE) of 4.59%, which is a good efficiency among inverted solar cells with an organic interlayer on an ITO cathode. The PCE shows a 79% increase in comparison to that of a bare ITO cathode, though the efficiency is lower than 5.13% for an inverted solar cell with an inorganic ZnO interlayer on ITO. Moreover, a conventional solar cell with a device configuration of ITO/PEDOT:PSS/active layer/PTPA-EP/Al could show a better PCE of 5.27%. The results indicate that PTPA-EP is a promising new cathode interlayer for high efficiency inverted and conventional solar cells. http://pubs.rsc.org/en/content/articlelanding/2012/jm/c1jm14970a#!divAbstract *
1/13/2014 15:29:45 * Pt‰ÛÒRu model catalysts for anodic methanol oxidation: Influence of structure and composition on the reactivity Harry Hoster, Teresa Iwasita, Hermann Baumg̤rtner and Wolf Vielstich Phys. Chem. Chem. Phys., 2001,3, 337-346 2001 * http://pubs.rsc.org/en/content/articlelanding/2001/cp/b004895j *
02/06/14 17:21 SKP5050 Hydrogen Detection by Polyaniline Nano•Âbers on Gold and Platinum Electrodes Jesse D. Fowler,‰Û  Shabnam Virji,‰Û  Richard B. Kaner,‰ÛÁ and Bruce H. Weiller J. Phys. Chem. C 2009, 113, 6444‰ÛÒ6449 2009 Polyaniline nano•Âbers were deposited on either gold or platinum electrodes and used as resistive sensors for the detection of hydrogen. In earlier work (J. Phys. Chem. B 2006, 110, 22266-22270), we showed that hydrogen interacts directly with polyaniline nano•Âbers to induce a small resistance decrease (-3%) at low concentrations of hydrogen (1%) using gold electrodes. This work showed that the sensor response on gold electrodes is due to hydrogen interaction with the polyaniline nano•Âbers. However, with platinum electrodes a much larger resistance increase (+65%) is observed under the same conditions. The sensor response on platinum electrodes is due to hydrogen interaction with platinum at the polyaniline-platinum interface. Hydrogen facilitates the formation of a Schottky barrier between platinum and polyaniline through a change in work function as platinum is converted to platinum hydride. The work function of polyaniline nano•Âbers was measured, and a model for sensor response is presented based on the relative work functions of the platinum, platinum hydride, and polyaniline nano•Âbers. Platinum hydride formation is fully reversible with the introduction of oxygen that converts the platinum hydride to water. The greater sensitivity of the platinum sensor can be used to detect hydrogen at a concentration of 10 ppm. http://pubs.acs.org/doi/pdf/10.1021/jp810500q *
02/06/14 17:27 RHC020 Hydrogen Detection by Polyaniline Nanofibers on Gold and Platinum Electrodes Jesse D. Fowler ‰Û , Shabnam Virji ‰Û , Richard B. Kaner ‰ÛÁ and Bruce H. Weiller *‰Û  J. Phys. Chem. C, 2009, 113 (16), pp 6444‰ÛÒ6449 2009 Polyaniline nanofibers were deposited on either gold or platinum electrodes and used as resistive sensors for the detection of hydrogen. In earlier work (J. Phys. Chem. B2006, 110, 22266‰öÕ22270), we showed that hydrogen interacts directly with polyaniline nanofibers to induce a small resistance decrease (‰öÕ3%) at low concentrations of hydrogen (1%) using gold electrodes. This work showed that the sensor response on gold electrodes is due to hydrogen interaction with the polyaniline nanofibers. However, with platinum electrodes a much larger resistance increase (+65%) is observed under the same conditions. The sensor response on platinum electrodes is due to hydrogen interaction with platinum at the polyaniline‰öÕplatinum interface. Hydrogen facilitates the formation of a Schottky barrier between platinum and polyaniline through a change in work function as platinum is converted to platinum hydride. The work function of polyaniline nanofibers was measured, and a model for sensor response is presented based on the relative work functions of the platinum, platinum hydride, and polyaniline nanofibers. Platinum hydride formation is fully reversible with the introduction of oxygen that converts the platinum hydride to water. The greater sensitivity of the platinum sensor can be used to detect hydrogen at a concentration of 10 ppm. http://pubs.acs.org/doi/abs/10.1021/jp810500q *
11/04/14 22:09 SKP5050 Role of Oxygen in the Work Function Modification at Various Stages of Chemically Synthesized Graphene Mukesh Mishra, Rakesh K. Joshi, Sunil Ojha, D. Kanjilal and T. Mohanty The Journal of Physical Chemistry C (117:38), 2013, pp. 19746-19750 2013 Correlation between the work function and oxygen content at various stages during synthesis of graphene by chemical route is presented. The values of work function in terms of contact surface potential difference (CPD) were estimated using a scanning Kelvin probe method. Oxygen content was determined using energy dispersive X-ray absorption (EDAX), and the data was further supported using the Rutherford back scattering method in oxygen resonance mode. Results indicated a linear correlation between the oxygen content and measured values of CPD at various stages during the chemical synthesis of graphene. http://pubs.acs.org/doi/abs/10.1021/jp406712s *
11/05/14 09:40 SKP5050 Alkyl Surface Treatments of Planar Zinc Oxide in Hybrid Organic/Inorganic Solar Cells C. G. Allen, D . J. Baker, T. M. Brenner, C. C. Weigand, J. M. Albin, K. X. Steirer, D. C. Olson, C. Ladam, D. S. Ginley, R. T. Collins and T. E. Furtak The Journal of Physical Chemistry C, (116:16), 2012, pp. 8872-8880 Apr-12 Hybrid organic/inorganic solar cells have not lived up to their potential because of poor interface properties. Interfacial molecular layers provide a way of adjusting these devices to improve their performance. We have studied a prototypical system involving poly(3-hexylthiophene) (P3HT) on planar zinc oxide (ZnO) films that have been modified with two types of molecules having identical 18-carbon alkyl chain termination and different surface attachments: octadecanethiol (ODT) and octadecyltriethoxysilane (OTES). We examined the functionalized surfaces using water contact angle measurements, Kelvin probe measurements, infrared absorbance spectroscopy, and atomic force microscopy. These have shown that OTES forms disordered incomplete monolayers, while ODT is prone to develop multilayered islands. Both treatments enhance polymer ordering. However, inverted solar cell devices fabricated with these treated interfaces performed very differently. ODT improves the short circuit current (JSC), open circuit voltage (VOC), and power conversion efficiency (ëá), while these parameters all decrease in devices constructed from OTES-treated ZnO. The differences in VOC are related to modifications of the surface dipole associated with deposition of the two types of alkyl molecules, while changes in JSC are attributed to a balance between charge transfer blocking caused by the saturated hydrocarbon and the improved hole mobility in the polymer. http://pubs.acs.org/doi/abs/10.1021/jp211692m *
11/04/14 20:59 SKP5050 Effect of Heterojunction on the Behavior of Photogenerated Charges in Fe3O4@Fe2O3 Nanoparticle Photocatalysts Xiao Wei, Tengfeng Xie, Linlin Peng, Wei Fu, Jiesheng Chen, Qian Gao, Guangyan Hong and Dejun Wang The Journal of Physical Chemistry C (115:17), 2011, pp. 8637-8642 Apr-11 The behavior of photogenerated charges in the Fe3O4@Fe2O3 core/shell nanoparticles with high photocatalytic activity have been investigated by surface photovoltage (SPV) spectroscopy and transient photovoltage (TPV) measurements. The single-phase Fe3O4 and Fe2O3 particles as references have been investigated simultaneously. The results demonstrate that the junction formation in the Fe3O4@Fe2O3 nanoparticles significantly affects the separation, transport, and recombination of photogenerated charges and even changes the transport direction and recombination velocity. And the mechanisms here have been discussed in detail. These results are helpful in understanding the photoelectric process of nanoscaled materials with the heterojunction structures and further utilizing the photoelectric materials and devices. http://pubs.acs.org/doi/abs/10.1021/jp111250z *
12/10/14 11:10 KP020 Polyethylenimine aqueous solution: a low-cost and environmental-friendly formulation to produce low‰ÛÒwork function electrodes for efficient easy-to-fabricate organic solar cells Xue Min, Fan gyuan Jiang, Fei Qin, Zaifang Li, Jinhui Tong, Sixing Xiong, Wei Meng and Yinhua Zhou ACS Appl. Mater. Interfaces, 2014 Dec-14 Polyethylenimine (PEI) has been widely used to produce low-work function electrodes. Generally, PEI‹ÛÛmodification is prepared by spin coating from 2-methoxyethanol solution. In this work, we explore the method for PEI modification on indium tin oxide (ITO) by dipping the ITO sample into PEI aqueous solution for organic solar cells. The PEI prepared in this method could reduce the work function of ITO as effective as prepared by spin coating from 2-methoxyethanol solution. H2O as the processing solvent is the most environmental-friendly and much cheaper comparing with the 2-methoxyethanol solvent. The dipping method is also compatible with large-area area samples. With low‰ÛÒwork function of ITO treated by dipping method, solar cells with a simple structure of glass/ITO/PEI(dipping)/P3HT:ICBA/ PEDOT:PSS (vacuum-free processing) display a high open-circuit voltage of 0.86 å± 0.01, a high fill factor of 66 å± 2%, and power conversion efficiency of 4.4 å± 0.3% under 100 mW/cm2 illumination. http://pubs.acs.org/doi/abs/10.1021/am5077974 *
02/10/15 09:59 SKP5050 An ITO-free polymer solar cell on flexible glass Nadia Formica, Paola Mantilla-Perez, Dhriti Sundar Ghosh, Davide Janner, Tong Lai Chen, Minghuang Huang, Sean Garner, Jordi Martorell and Valerio Pruneri ACS Applied Materials and Interfaces, 2015 2015 Future opto electronic devices and their low cost roll-to-roll production require mechanically flexible transparent electrodes (TEs) and substrate materials. Indium tin oxide (ITO) is the most widely used TE thanks to its high optical transmission and low electrical sheet resistance. However ITO, besides being expensive, has very poor performance under mechanical stress due to its fragile oxide nature. Alternative TE materials have thus being searched. Here we report the development of a multilayer TiO2/Ag/Al doped ZnO (AZO) TE structure and an ITO-free polymer solar cell (PSC) incorporating it. Electro-optical performances close to those of ITO can be achieved for the proposed TE and corresponding PSC with the additional advantage of being mechanically flexible, as it is demonstrated by the fact that the cell efficiency maintains 94% of its initial value (6.6%) after 400 cycles of bending, with 6 and 3 cm maximum and minimum radii, respectively. Instead of common plastic materials, our work uses a very thin (0.14 mm) flexible glass substrate with several benefits, such as the possibility of high temperature processes, superior anti-permeation properties against oxygen, moisture and improved film adhesion. http://pubs.acs.org/doi/abs/10.1021/am5071909 *
02/06/14 17:15 * Applying the Kelvin probe to biological tissues: Theoretical and computational analyses Andrew C. Ahn1,*,‰Û , Brian J. Gow1,‰Û , Ì÷rjan G. Martinsen2,3, Min Zhao4,5, Alan J. Grodzinsky6, and Iain D. Baikie7 American Physical Society 2012 The Kelvin probe measures surface electrical potential without making physical contact with the specimen. It relies on capacitive coupling between an oscillating metal tip that is normal to a specimen's surface. Kelvin probes have been increasingly used to study surface and electrical properties of metals and semiconductors and are capable of detecting material surface potentials with submillivolt resolution at a micrometer spatial scale. Its capability for measuring electrical potential without being confounded by electrode-specimen contact makes extending its use towards biological materials particularly appealing. However, the theoretical basis for applying the Kelvin probe to dielectric or partially conductive materials such as biological tissue has not been evaluated and remains unclear. This study develops the theoretical basis underlying Kelvin probe measurements in five theoretical materials: highly conductive, conductive dielectric with rapid charge relaxation, conductive dielectric with slow charge relaxation, perfect dielectric, and tissue with a bulk serial resistance. These theoretically derived equations are then computationally analyzed using parameters from both theoretical specimens and actual biomaterials‰ÛÓincluding wet skin, dry skin, cerebrospinal fluid, and tendon. Based on these analyses, a Kelvin probe performs in two distinct ways depending on the charge relaxation rates of the sample: The specimen is treated either as a perfect dielectric or as highly conductive material. Because of their rapid relaxation rate and increased permittivity biomaterials behave similarly to highly conductive materials, such as metal, when evaluated by the Kelvin probe. These results indicate that the Kelvin probe can be readily applied to studying the surface potential of biological tissue. http://pre.aps.org/abstract/PRE/v85/i6/e061901 *
02/06/14 17:17 SKP5050 Tunable work function in MgO/Nb:SrTiO3 surfaces studied by Kelvin probe technique Tomofumi Susaki*, Asahi Makishima, and Hideo Hosono‰Û  American Physical Society 2010 We studied the work function of Nb 0.5-wt % doped SrTiO3 (Nb:SrTiO3) (100) substrates covered with MgO thin films by Kelvin probe contact potential technique. The work function of MgO/Nb:SrTiO3 was reduced as a sharp function of MgO film thickness up to 1 nm while it remained almost constant beyond 1 nm. The amount of work-function reduction by depositing 5-nm-thick MgO film was ‰ö¼0.6 eV when grown under oxygen partial pressure, p(O2), of 10+1 Pa and increased up to ‰ö¼1 eV when grown at p(O2) = 10‰öÕ3 Pa. Atomic force microscopy and in-plane x-ray-diffraction measurements indicated the formation of tighter interface when grown under oxygen poor conditions. Both a sharp work-function reduction with MgO deposition and its modification by how firmly the interface was formed were consistent with the electron compression model that the metal work function could be modified when covered by insulating films to block the metal electrons. The present work demonstrated that metal work function could be tuned by depositing insulating films with the film thickness and the interfacial tightness controlled. http://prb.aps.org/pdf/PRB/v83/i11/e115435 *
02/06/14 17:26 RHC030 Comprehensive picture of p-type doping of P3HT with the molecular acceptor F4TCNQ P. Pingel and D. Neher* PHYSICAL REVIEW B 87, 115209 (2013) 2013 By means of optical spectroscopy, Kelvin probe, and conductivity measurements, we study the p-type doping of the donor polymer poly(3-hexylthiophene), P3HT, with the molecular acceptor tetrafluorotetracyanoquinodimethane, F4TCNQ, covering a broad range of molar doping ratios from the ppm to the percent regime. Thorough quantitative analysis of the specific near-infrared absorption bands of ionized F4TCNQ reveals that almost every F4TCNQ dopant undergoes integer charge transfer with a P3HT site. However, only about 5% of these charge carrier pairs are found to dissociate and contribute a free hole for electrical conduction. The nonlinear behavior of the conductivity on doping ratio is rationalized by a numerical mobility model that accounts for the broadening of the energetic distribution of transport sites by the Coulomb potentials of ionized F4TCNQ dopants. http://prb.aps.org/abstract/PRB/v87/i11/e115209 *
02/06/14 17:20 SKP5050 Work function engineering via LaAlO3/SrTiO3 polar interfaces Tomofumi Susaki*, Asahi Makishima, and Hideo Hosono‰Û  American P hysical Society 2011 By in situ Kelvin probe measurement combined with pulsed laser deposition, we have observed a change in the work function of (Nb:)SrTiO3(100) as LaAlO3(100) polar film is deposited, which strongly depends on the termination of the SrTiO3(100) surface and on the presence of the insulating SrTiO3(100) buffer layer. A sharp work function drop with LaAlO3(100) film deposition on a TiO2-terminated SrTiO3(100) surface would indicate the contribution of high-density electron gas at the interface to the unusual work function lowering. The present finding demonstrates that insulator-on-insulator structures using polar films could be a powerful platform to design artificial electronic states. http://prb.aps.org/abstract/PRB/v84/i11/e115456 *
1/13/2014 15:05:57 SKP5050 Object size effect on the contact potential difference measured by scanning Kelvin probe method B.Polyakov1, R.Krutokhvo stov1, A.Kuzmin1, E.Tamanis2, I.Muzikante1, I.T ale1 * 2010 Contact potential difference (CPD) was measured by macroscopic Kelvin probe instrument and scanning Kelvin probe microscope on Al, Ni and Pt on ITO substrates at ambient conditions. CPD values measured by scanning Kelvin probe microscope and macroscopic Kelvin probe are close within the error of about 10-30% for large studied objects, whereas scanning Kelvin probe microscope signal decreases, when the object size becomes smaller than 1.4 ë¼m. CPD and electric field signals measured using many-pass technique allowed us to estimate the influence of electrostatic field disturbance, especially, in the case of small objects. Keywords: work function, contact potential measurement, electric field measurement, Kelvin probe, Scanning probe microscopy, imaging of surface electrical properties, surface interfacial characterization, microelectronic characterization http://peer.ccsd.cnrs.fr/docs/00/60/66/42/PDF/PEER_stage2_10.1051%252Fe pjap%252F2010088.pdf *
11/05/14 09:15 SKP5050 Impact of Electrode Roughness on Metal-Insulator-Metal (MIM) Diodes and Step Tunneling in Nanolaminate Tunnel Barrier Metal-Insulator-Insulator-Metal (MIIM) Diodes John F. Conl ey Jr., Nasir Alimardani Rectenna Sol ar Cells (Part II), 2013, pp. 111-134 Jul-13 In this chapter, the impact of electrode roughness and bilayer insulator tunnel barriers on the performance of metal-insulator-metal (MIM) diodes are discussed. The effect of bottom electrode roughness on the current versus voltage (I‰ÛÒV) characteristics of asymmetric electrode M1IM2 tunnel diodes is discussed first. Atomic layer deposition (ALD) is used to deposit high quality insulators independent of bottom metal electrode. It is shown that bottom electrode roughness can strongly influence the I‰ÛÒV characteristics of M1IM2 diodes, overwhelming even the metal work function difference induced asymmetry. Devices with smoother bottom electrodes are shown to produce I‰ÛÒV behavior with better agreement with Fowler‰ÛÒNordheim tunneling theory as well as yield a higher percentage of well-functioning devices. By combining high quality uniform tunnel barriers deposited by ALD with atomically smooth (~0.3 nm RMS roughness) bottom electrodes, highly nonlinear and asymmetric MIM tunnel diodes with good reproducibility and stable I‰ÛÒV behavior are produced. Next, the impact of nanolaminate bilayer insulator tunnel barriers on asymmetric metal work function metal-insulator-insulator-metal (M1I1I2M2 & M1I2I1M2) devices is discussed. It is demonstrated that bilayer tunnel barriers can be arranged to either enhance, oppose, or even reverse the asymmetry induced by the asymmetric work function electrodes. These results represent experimental demonstration that step tunneling (a step change in the tunneling distance through a bilayer tunnel barrier) can dominate the I‰ÛÒV asymmetry of M1IIM2 diodes with asymmetric work function electrodes. By combining bilayer tunnel barriers with asymmetric metal electrodes, devices are made with voltage asymmetry and nonlinearity that exceed that of standard single layer asymmetric electrode M1IM2 devices as well as that of symmetric electrode M1I1I2M1 devices. http://link.springer.com/chapter/10.1007/978-1-4614-3716-1_6 *
11/05/14 11:26 KP020 Reusing of transmitted light by localized surface plasmon enhancing of Ag nanoparticles in organic solar cells Chao Wang, Wen-jing Qin, Chun-yu Ma, Qiang Zhang, Li-ying Yang and Shou-gen Yin Optoelectro nics Letters (8:6), 2012, pp.401-404 Nov-12 Silver nanop articles (Ag NPs) are synthesized with chemical method, which are introduced into the traditional organic photovoltaic (OPV) structure. The experimental results show that both the optical and photoelectric properties are enhanced because of localized surface plasmon (LSP) effects of Ag NPs. The advantage of adding Ag NPs behind active layer in incident direction is discussed. We believe this route can avoid absorption shadow and enhance the reusing of transmitted light of active layer. The average short-circuit current (J SC) of the optimum device can be raised from 9.23 mA/cm2 to 10.84 mA/cm2, and the energy converting efficiency (PCE) can be raised from 3.22% to 3.85%. http://link.springer.com/article/10.1007/s11801-012-2326-2 *
11/04/14 21:52 SKP5050 Improved Thermoelectric Properties of Se-Doped n-Type PbTe1‰öÕx Se x (0 ‰ä¤ x ‰ä¤ 1) Ranita Basu, S. Bhattacharya, Ranu Bhatt, Ajay Singh, D. K. Aswal and S. K. Gupta Journal of electronic Materials (42:7), 2013, pp.2292-2296 Jun-13 Enhancement of the thermoelectric figure of merit is of prime importance for any thermoelectric material. Lead telluride has received attention as a potential thermoelectric material. In this work, the effect of Se substitution has been systematically investigated in PbTe1‰öÕx Se x . The thermoelectric properties of synthesized alloys were measured in the temperature range of 300 K to 873 K. For the particular composition of x = 0.5, ë± was highest at ~292 ë¼V/K, while k was lowest at ~0.75 W/m-K, resulting in the highest dimensionless figure of merit of ZT ‰äö 0.95 at 600 K. The increase in thermopower for x = 0.5 can be attributed to the high distortion in the crystal lattice which leads to the formation of defect states. These defect states scatter the majority charge carriers, leading to high thermopower and high electrical resistivity. The dramatic reduction of the thermal conductivity for x = 0.5 can be attributed to phonon scattering by defect states. http://link.springer.com/article/10.1007/s11664-013-2645-5 *
02/10/15 10:18 SKP5050 Interface characteristics for graphene contact to n-type and p-type GaN observed by X-ray photoelectron spectroscopy Chia-Lung Tsai, Yow-Jon Lin, Jian-Huang Lin Journal of Materials Science: Materials in Electronics, 2015 2015 The interface characteristics of graphene/GaN samples using X-ray photoelectron spectroscopy (XPS) measurements are investigated. XPS makes it possible to extract a reliable barrier-height value. For graphene/n-type GaN (graphene/p-type GaN) samples, the Schottky barrier height is 0.85 (2.50) eV. To determine the Fermi-level pinning/unpinning at the graphene/GaN interfaces, an analysis is conducted according to the Schottky‰ÛÒMott limit. It is shown that the Fermi energy level is unpinned and the barrier-height value is dependent on the work function of graphene. Investigation of graphene/GaN interfaces is important, and providing the other technique for surface potential control is possible. http://link.springer.com/article/10.1007/s10854-015-2796-7 *
11/04/14 14:40 SKP5050 Electrical and optoelectronic properties of graphene Schottky contact on Si-nanowire arrays with and without H202 treatment Jian-Jhou Ze ng and Yow-Jon Lin Applied Physics A: Materials Science and Processing (116:2), 2014, pp. 581-587. Aug-14 Developing better contacts on Si-nanowire (SiNW) arrays is one of the main challenges for Si-based device technology. The present work reports the fabrication and detailed electrical properties of graphene/SiNWs/n-type Si Schottky diodes. The graphene/H2O2-treated SiNWs/n-type Si Schottky diode shows a better rectifying behavior in the dark than the graphene/SiNWs/n-type Si diode. Such an improvement indicates that a good passivation is formed at the interface. The graphene/H2O2-treated SiNWs/n-type Si Schottky diode also shows a higher photocurrent under illumination than the graphene/SiNWs/n-type Si diode. Results revealed that SiNW surface passivation influences the photoconductivity by reducing the number of electron traps that serve to decrease the photocurrent time constant. http://link.springer.com/article/10.1007/s00339-013-8157-6 *
11/04/14 21:15 SKP5050 Enhanced surface photovoltage response of ZnO nanorod based inorganic/organic hybrid junctions by constructing embedded bulk composite structures Dawei Kang, Aimin Liu, Jiming Bian, Zengquan Hu, Yiting Liu and Fen Qiao Applied Physics A (110:2), 2013, pp.263-267 Feb-13 Two kinds of inorganic/organic hybrid junctions based on ZnO nanorods (NRs), i.e. two-layer planar heterojunction and embedded bulk composite structures, were fabricated on ITO glass substrates. Surface photovoltage (SPV) methods based on a Kelvin probe and a lock-in amplifier were respectively utilized to study the photogenerated charges at the surface and the interface in the ZnO-based hybrid junctions. Results indicate that the lock-in SPV response of the bulk composite structure is much higher than its planar counterpart in terms of intensity and spectral range. Therefore, ZnO NR/PF (poly(9,9-di-n-octylfluorenyl-2,7-diyl)) embedded bulk composite structures are more suitable and preferred for photovoltaic application. http://link.springer.com/article/10.1007/s00339-012-7314-7 *
03/12/15 10:16 SKP5050 General method to synthesize ultrasmall metal oxide nanoparticle suspensions for hole contact layers in organic photovoltaic devices Yun-Ju Lee, J ian Wang, Julia W. P. Hsu and Diego Barrera MRS Communications 2015 Mar-15 Solution-Processed hole contact layers (HCLs) of metal oxide nanoparticle (NP) films improve performance of organic photovoltaics (OPVs), but have thus far required harsh post-deposition thermal or plasma treatments. Here, we describe a general method to synthesize suspensions of ultrasmall (1‰ÛÒ2 nm) MoO3, WO3, NiO x, and CoO x NPs in n-butanol. Spin-coated metal oxide NP films with no post-deposition treatment exhibit high work function and ionization energy consistent with the oxidation states of the metal cations. Metal oxide NP HCLs demonstrate performance matching those of reference conventional and inverted OPVs containing PEDOT:PSS and evaporated MoO3. http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9579277&fileId=S2159685915000051 *
11/04/14 22:05 SKP5050 X-ray photoelectron spectroscopy studies of indium-tin-oxide treated via oxygen plasma immersion ion implantation Long He, Zho nghang Wu, Zebin Li, Qiongrong Ou and Rongqing Liang The European Physical Journal Applied Physics (62:3), 2013 Jun-13 Surface modification was performed on the indium-tin-oxide (ITO) thin films by oxygen inductive coupling plasma (O-ICP) and oxygen plasma immersion ion implantation (O-PIII). The electronic states of ITO surfaces were characterized by X-ray photoelectron spectroscopy (XPS). The observed peak shifts of O 1s, In 3d5/2 and Sn d5/2 core levels showed that the work function of ITO can be further enhanced by O-PIII treatment, compared with that of untreated and O-ICP treated surfaces. The deconvolution of O 1s spectrum and calculation of stoichiometry showed that the work function improvement should be attributed to the increase of effective oxygen content, namely, the elimination of oxygen vacancies. In addition, the measurement of Kelvin probe confirmed that an increment of the ITO work function by 1.1 eV was obtained on O-PIII treated sample and the results sustained our proposal. http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8937008&fileId=S1286004213400381 *
11/19/2014 16:06:09 * Ion-induced electrostatic charging of ice at 15‰ÛÒ160 K J. Shi, M. Fa må«a, B. D. Teolis and R. A. Baragiola PHYSICAL REVIEW B 85, (2012), 035424 Jan-12 We studied electrostatic charging of ice films induced by the impact of 1‰öÕ200-keV Ar+ ions and their subsequent discharging postirradiation. We derived the positive surface electrostatic potential from the kinetic energy of sputtered molecular ions and with a Kelvin probe. Measurements were performed as a function of film thickness, temperature, and ion energy. Charging requires that the projectile ions are stopped in the ice and that the ice temperature is below 160 K. The decay of the electrostatic charge after irradiation is determined by two time constants, corresponding to the detrapping of trapped charges in shallow and deep traps within the ice. Amorphous solid water films are found to charge to a higher electrostatic potential than crystalline ice films. The surface potential of crystalline ice increases and decreases during cooling and warming, respectively, without hysteresis. We present a model to describe the charging and discharging processes. http://journals.aps.org/prb/abstract/10.1103/PhysRevB.85.035424 *
11/05/14 11:33 KP020 Influence of CuxS back contact on CdTe thin film solar cells Lei Zhi, Feng Lianghuan, Zeng Guanggen, Li Wei, Zhang Jingquan, Wu Lili and Wang Wenwu Journal of Semiconductors (34:1), 2013, 014008 Jan-13 We present a detailed study on CuxS polycrystalline thin films prepared by chemical bath method and utilized as back contact material for CdTe solar cells. The characteristics of the films deposited on Si-substrate are studied by XRD. The results show that as-deposited CuxS thin film is in an amorphous phase while after annealing, samples are in polycrystalline phases with increasing temperature. The thickness of CuxS thin films has great impact on the performance of CdS/CdTe solar cells. When the thickness of the film is about 75 nm the performance of CdS/CdTe thin film solar cells is found to be the best. The energy conversion efficiency can be higher than 12.19%, the filling factor is higher than 68.82% and the open-circuit voltage is more than 820 mV. http://iopscience.iop.org/1674-4926/34/1/014008 *
11/05/14 11:40 KP020 Effect of NaCl doped into Bphen layer on the performance of tandem organic light-emitting diodes Xiao Zhi-Hui, Wu Xiao-Ming, Hua Yu-Lin, Bi Wen-Tao, Wang Li, Zhang Xin, Xin Li-Wen and Yin Shou-Gen Chinese Physics B (23:8), 2014, 087811 2014 To improve the performance of tandem organic light-emitting diodes (OLEDs), we study the novel NaCl as n-type dopant in Bphen:NaCl layer. By analyzing their relevant energy levels and carrier transporting characteristics, we discuss the mechanisms of the effective charge generation layer (CGL) of Bphen:NaCl (6 wt%)/MoO3. In addition, we use the Bphen:NaCl (20 wt%) layer as the electron injection layer (EIL) combining the CGL to further improve the performance of tandem device. For this tandem device, the maximal current efficiency of 9.32 cd/A and the maximal power efficiency of 1.93 lm/W are obtained, which are enhanced approximately by 2.1 and 1.1 times compared with those of the single-emissive-unit device respectively. We attribute this improvement to the increase of electron injection ability by introducing of Bphen:NaCl layer. Moreover, the CGL is almost completely transparent in the visible light region, which is also important to achieve an efficient tandem OLEDs. http://iopscience.iop.org/1674-1056/23/8/087811 *
11/04/14 21:56 SKP5050 Enhanced work Function of Al-Doped Zinc-Oxide Thin Films by Oxygen Inductively Coupled Plasma Treatment Li Zebin, Wu Zhonghang, Ju Jiaqi, He Kongduo, Chen Zhenliu, Yang Xilu, Yan Hang, Ou Qiongrong and Liang Rongqing Plasma Scien ce and Technology (16:1), 2014 2014 Al-doped zin c-oxide (AZO) thin films treated by oxygen and chlorine inductively coupled plasma (ICP) were compared. Kelvin probe (KP) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the effect of treatment. The results of KP measurement show that the surface work function of AZO thin films can increase up to 5.92 eV after oxygen ICP (O-ICP)'s treatment, which means that the work function was increased by at least 1.1 eV. However, after the treatment of chlorine ICP (Cl-ICP), the work function increased to 5.44 eV, and the increment was 0.6 eV. And 10 days later, the work function increment was still 0.4 eV after O-ICP's treatment, while the work function after Cl-ICP's treatment came back to the original value only after 48 hours. The XPS results suggested that the O-ICP treatment was more effective than Cl-ICP for enhancing the work function of AZO films, which is well consistent with KP results. http://iopscience.iop.org/1009-0630/16/1/17 *
11/04/14 15:03 SKP5050 A study of the dynamic properties of photo-induced charge carriers at nanoporous TiO2/conductive substrate interfaces by the transient photovoltage technique Xiao Wei, Te ngfeng Xie, Dan Xu, Qidong Zhao, Shan Pang and Dejun Wang Nanotechnology (19:27), 2008, 275707 2008 Two interfaces with opposite orientations of the built-in electric field, nanoporous TiO2 film/ FTO electrode and nanoporous TiO2 film/semitransparent Pt substrate, were constructed. The separation and transport of photo-induced charge carriers in the two systems of nanoporous TiO2/conductive substrate were studied by the transient photovoltage technique. Various transient photovoltage responses were obtained when the laser beam was incident from the surface of the nanoporous TiO2 film (top illumination) or the TiO2/substrate interface (bottom illumination). A linear and a logarithmic dependence of the photovoltage amplitude on the excitation level were observed for top illumination and bottom illumination, respectively. The results indicate that diffusion is the major way for the separation of charge carriers in the nanoporous TiO2 film and that the excess carriers were separated by drift under the built-in electric field at the TiO2/substrate interfaces. http://iopscience.iop.org/0957-4484/19/27/275707 *
11/05/14 11:48 KP020 A Simple Interconnection Layer for Tandem Organic Solar Cells with Improved Efficiency and Fill Factor Zheng Ke-Ning, Yang Li-Ying, Cao Huan-Qi, Qin Wen-Jing and Yin Shou-Gen Chinese Physics Letters (31:6), 2014, 068801 Jun-14 We demonstrate a simple interconnection layer (ICL) that can be employed in tandem organic solar cells. An ICL with an optimized structure of Ca/Au/MoO3 is used between two sub cells composed of identical regioregularpoly(3-hexylthiophen) (P3HT):[6,6]-phenyl C61-butyric acid methylester (PCBM) photoactive layers. Power conversion efficiency (PCE) of 3.24% and fill factor (FF) of 68.0% are achieved with such an ICL under simulated sunlight (100 mW.cm‰öÕ2). Compared with the best values of devices with ICLs of Ca/Al/MoO3, PCE is improved by 68.9% and FF is improved by 15.5%. The improved performances are attributed to the optical and electrical balances in both sub cells. The presented ICL extracts free charges efficiently from both sub cells thereby suppressing the exaction recombination in each sub cell. http://iopscience.iop.org/0256-307X/31/6/068801 *
11/05/14 11:17 KP020 Enhanced Performance and Stability in Polymer Photovoltaic Cells Using Ultraviolet-Treated PEDOT:PSS Xu Xue-Jian, Yang Li-Ying, Tian Hui, Qin Wen-Jing, Yin Shou-Gen and Zhang Fengling Chinese Physics Letters (30:7), 2013, 077201 2013 We investigate the effects of ultraviolet (UV) irradiation treatment with varying irradiation intensities for different treatment times of poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film on the performance and stability of polymer solar cells (PSCs) based on regioregular poly(3-hexylthiophene) (P3HT) and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend. Ultraviolet-visible transmission spectra, x-ray photoelectron spectroscopy, contact angle measurement, atomic force microscopy and the Kelvin probe method are conducted to characterize the UV-treated PEDOT:PSS film. The results demonstrate that UV treatment can improve the power conversion efficiency (PCE) and stability of PSCs effectively. The best performance is achieved under 1200 ë¼W/cm2 UV treatment for 50 min. Compared to the control device, the optimized device exhibits enhanced performance with a Voc of 0.59 V, Jsc of 12.3 mA/cm2, fill factor of 51%, and PCE of 3.64%, increased by 3.5%, 33%, 8.7% and 50%, respectively. The stability of the PSCs is enhanced by 2.5 times simply through the UV treatment on the PEDOT:PSS buffer layer. The improvement in the device performance and stability is attributed to the improvement in the wettability property and the increase in the work function of the PEDOT:PSS film by UV treatment, while the impact of UV treatment on the transparency of the PEDOT:PSS film is negligible. The strategy of using UV treatment to improve device performance and stability is attractive due to its simplicity, cost-effectiveness, and because it is suitable for large-scale commercial production. http://iopscience.iop.org/0256-307X/30/7/077201 *
1/13/2014 15:07:32 * High vacuum cells for classical surface techniques Martinez, Im ee Su, Baldelli, Steven Review of Scientific Instruments (Volume 81, Issue 4, 2010) 2010 Novel glass cells were designed and built to be able to perform surface potential and surface tension measurements in a contained environment. The cells can withstand pressures of approximately 1Ì—10-6 Torr, providing a reasonable level of control in terms of the amounts of volatile contaminants during experimentation. The measurements can take several hours; thus the cells help maintain the integrity of the sample in the course of the experiment. To test for the feasibility of the cell design, calibration measurements were performed. For the surface potential cell, the modified TREK 6000B-7C probe exhibited performance comparable to its unmodified counterpart. The correlation measurements between applied potential on the test surface and the measured potential showed R-values very close to 1 as well as standard deviation values of less than 1. Results also demonstrate improved measurement values for experiments performed in vacuum. The surface tension cell, on the other hand, which was used to perform the pendant drop method, was tested on common liquids and showed percentage errors of 0.5% when compared to literature values. The fabricated cells redefine measurements using classical surface techniques, providing unique and novel methods of sample preparation, premeasurement preparation, and sample analysis at highly beneficial expenditure cost. http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5442928 *
11/04/14 16:43 SKP5050 Novel recom bination lifetime mapping technique through Kelvin probe studies Alderman, N ., Danos, L., Grossel, M. and Markvart, T. Photovoltaic Specialists Conference (PVSC), 2013, IEEE 39th Jun-13 The Kelvin probe is a very powerful and versatile tool, allowing the extraction of data such as diffusion length, surface photovoltage and impurity concentrations. This paper investigates the extraction of surface recombination velocities (and assuming a bulk lifetime, the surface recombination lifetime) from the I-V type dependence of the sample. By using an X-Y stage, the surface recombination lifetime can be imaged for entire wafers, instead of obtaining an average value of lifetime similar to that obtained from the Sinton WCT-120 lifetime tool. This is useful in determining where further improvements in the surface passivation can be obtained, by observing problem areas in the passivation layer. http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6744132&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6744132 *
11/04/14 17:03 SKP5050 An argument for the importance of material property characterization of hydrogels Zuidema, J. M. and Gilbert, R. J. Bioengineering Conference (NEBEC), 2011, IEEE 37th Annual Northeast Apr-11 Hydrogels are being fabricated for use in many tissue engineering applications. In order to advance the field, material properties must be characterized to determine the most desirable attributes. The data presented shows the importance of both surface charge and mechanical properties on dorsal root ganglia neurite extension. http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5778695&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5778695 *
11/04/14 14:21 SKP5050 Surface investigation by using a Scanning Kelvin Probe Halek, G., Baikie, I. D. and Teterycz, H. Students and Young Scientists Workshop, 2010 IEEE International, pp. 24-27 Jun-10 In this paper we present the relative work function measurements of Platinum (Pt), Molybdenum (Mo), Lead (Pb), and Graphite (C) by using Kelvin Probe. The obtained results have shown that the work function measurements made in air are affected by the adsorption of oxygen. To measure the ‰ÛÏtrue‰Û metal work function the oxide layer has to be removed. Moreover in the experiments we measured the work function changes of a platinum sample after mechanically cleaning of the surface and exposure to air. The decrease in the work function leads to the conclusion that a positive outwards dipole layer on the surface is created. http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5714161&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5714161 *
11/05/14 12:22 KP020 Defect Generation at Charge-Passivated \hbox {Si} ‰ÛÒ \hbox {SiO}_{2} Interfaces by Ultraviolet Light Black, Lachlan E. and McIntosh, K.R. Electron Devices, IEEE Transactions on (57:8), 2010, pp. 1996-2004. Aug-10 The effect of surface charge on defect generation at the Si-SiO2 interface by UV radiation is investigated. The surface charge is deposited by the corona method, and photoconductance and Kelvin probe measurements are used to characterize surface recombination and surface charge density. Both electron injection and defect generation are found to occur for significantly lower photon energies in the presence of a positive surface charge, with evidence that photons with an energy less than 3.66 eV are capable of generating interface defects. In contrast to previous studies on MOS structures, the majority of the defect generation is found to occur at oxide fields less than ~ 1 MV/cm. A possible explanation is discussed in terms of the hydrogen-release model of the defect generation. These results have significant relevance to high-efficiency silicon solar cells. http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5497128&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5497128 *
11/05/14 11:23 KP020 Realization of Low Driving Voltage in Organic Light-Emitting Diodes Using C60 as an Electron Transport Layer and Alq3 as a Buffer Layer Xiao Ming W u, Xue Mu, Yu Lin Hua, Juan Juan Bai, Li Wang, Zhi Hui Xiao, Ni Dong and Shou Gen Yin Electron Device Letters, IEEE, (34:5), 2013, pp. 650-652 May-13 Organic light -emitting diodes with low driving voltage based on fullerene (C60) as an electron transport layer and tris (8-hydroxyquinolinato)-aluminum (Alq3) as a buffer layer are successfully fabricated. For the optimal device with structures of ITO/NPB (40 nm)/Alq3 /(30 nm)/C60 (20 nm)/Alq3 (3 nm)/LiF (0.8 nm)/Al (120 nm), the turn-on driving voltage is 2.8 V, which is reduced 0.4 V compared with that of the control device. Meanwhile, the driving voltage of 4.9 V has been achieved at a luminance of 1000 cd/m2 in this device, which is reduced 1.8 V compared with that of the control device. The results have a significant effect on the commercialization application of the devices. http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6496151&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6496151 *
11/04/14 15:39 SKP5050 Stability and bias stressing of metal/insulator/metal diodes Alimardani, N., Conley, J. F., Cowell, E. W., Wager, J. F., Chin, M., Kilpatrick, S. and Dubey, M. Integrated Reliability Workshop Final Report (IRW), 2010 IEEE International pp. 80-84 Oct-10 The perform ance and stability of metal/insulator/metal tunnel diodes was investigated as a function of interfacial roughness using Al, Ir, Pt, and ultra-smooth amorphous multi-metal (ZrCuAlNi) bottom electrodes with uniform Al2O3 tunnel dielectrics deposited via atomic layer deposition. Current density versus field behavior and device yield were found to be a function of interfacial roughness with smoother electrodes exhibiting more ideal behavior and higher percentages of working devices. A preliminary investigation of DC bias stressed devices suggests that interfacial roughness plays a large role in stability and reliability as well. http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=5706491&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5706491 *
02/06/14 16:59 RHC020 AN INVESTIG ATION OF GERMANIUM COATED BLACK KAPTON AND UPILEX FILMS UNDER DIFFERENT ENVIRONMENTAL GROUND CONDITIONS Virginie CÌ© sar-Auguste (1), Yuriy Butenko(1), Andreas Polsak (1), Thomas Rohr(1), Christopher Semprimoschnig (1), Ton de Rooij (2), Marc Van Eesbeek (1) ESA-ESTEC, Materials Space Evaluation & Radiation Effects Section 2008 Recently, blo tch-like darkening on Germanium coated polyimide films was found after apparent storage in a controlled cleanroom environment. Whereas the limited stability of Germanium coatings in air is generally recognized, the severity of the degradation within a relatively short time frame triggered this investigation on the long-duration stability of Germanium coatings. Three different Germanium coated polyimide films, black Kapton, Upilex S and Upilex S/VDA, have been studied under different storage conditions with controlled temperature, humidity level, and oxygen content over a period of one year. Evidently, increasing relative humidity as well as temperature accelerated the Germanium degradation process. In order to understand the degradation of Germanium under these conditions, several measurements have been performed at the beginning of the test, at some inspection points and at the end of the test campaign. Visual inspections, thermo-optical measurements, Scanning Electron Microscopy (SEM) and Kelvin probe measurements were performed. http://esmat.esa.int/Materials_News/ISME09/pdf/3-Ground/Poster%20Groung%20Testing%20-%20Cesar-Auguste.pdf *
2/16/2015 9: 12:30 SKP5050 Plasma processing of Nb surfaces for SRF cavities P. V. Tyagi, R. Afanador, M. Doleans, S-H. Kim and C. McMahan Proceedings of LINAC2014, 2014 2014 Field emission is one of the most critical issues to achieve high performances of niobium (Nb) superconducting radio frequency (SRF) cavities. Field emission is mainly related to contaminants present at top surface of SRF cavities that act as electron emitters at high gradient operation and limit the cavity accelerating gradient. An R&D program at the Spallation Neutron Source (SNS) is in place [1, 2] aiming to develop an in-situ plasma processing technique to remove some of the residual contaminants from inner surfaces of Nb cavities and improve their performance. The plasma processing R&D has first concentrated on removing hydrocarbon contamination from top surface of SRF cavities. Results from the surface studies on plasma processed Nb samples will be presented in this article and showed the removal of hydrocarbons from Nb surfaces as well as improvement of the surface workfuntion (WF). http://accelconf.web.cern.ch/AccelConf/LINAC2014/papers/mopp115.pdf *
1/13/2014 15:13:54 * Effects of the strain rate of prior deformation on the wear-corrosion synergy of carbon steel Yin, S., Li, D. and Bouchard, R. METALLURGICAL AND MATERIALS TRANSACTIONS A (263), 2007, pp. 801 - 807. 2007 * * *
1/13/2014 15:14:07 * Effects of the strain rate of prior deformation on the wear-corrosion synergy of carbon steel Yin, S., Li, D. and Bouchard, R. METALLURGICAL AND MATERIALS TRANSACTIONS A (263), 2007, pp. 801 - 807. 2007 * * *
1/13/2014 15:13:21 * Prediction of elastic-contact friction of transition metals under light loads based on their electron work functions, Electrochemical characterization of Si(111) modified with linear and branched alkyl chains, Li, Y. and Li, D. JOURNAL OF PHYSICS D-APPLIED PHYSICS (40:19), 2007, pp. 5980 - 5983. 2007 * * *
1/13/2014 15:16:23 * Size- and ori entation-dependent photovoltaic properties of ZnO nanorods, Zhao, Q. D., Xie, T. F., Peng, L. L., Lin, Y. H., Wang, P., Peng, L. and Wang, D. J. JOURNAL OF PHYSICAL CHEMISTRY C (111:45), 2007, pp. 17136--17145. 2007 * * *
1/13/2014 15:13:05 * Electrochemi cal characterization of Si(111) modified with linear and branched alkyl chains, Bin, X. M., M ischki, T. K., Fan, C. Y.,, G. P. and Wayner, D. D. M. JOURNAL OF PHYSICAL CHEMISTRY C (111:36), 2007, pp. 13547--13553. 2007 * * *
1/13/2014 15:13:42 * Induced incr ease in surface work function and surface energy of indium tin oxide-doped ZnO films by (NH4)(2)S-x treatment," Tsai, C., Lin, Y., Wu, P., Chen, S., Liu, D., Hong, J., Liu, C., Shih, Y., Cheng, J. and Chang, H JOURNAL OF APPLIED PHYSICS (101:11), 2007, pp. 113713. 2007 * * *
1/13/2014 15:14:34 * Surface photovoltage study of photogenerated charges in ZnO nanorods array grown on ITO, Zhao, Q., Wa ng, D., Peng, L., Lin, Y., Yang, M. and Xie, T. CHEMICAL PHYSICS LETTERS (434:1-3), 2007, pp. 96 - 100. 2007 * * *
1/13/2014 15:14:19 * Poly(3,3 '''-di dodecylquarterthiophene) field effect transistors with single-walled carbon nanotube based source and drain electrodes Zhang, Y., Sh i, Y., Chen, F., Mhaisalkar, S., Li, L., Ong, B. and Wu, Y. APPLIED PHYSICS LETTERS (91:22), 2007, pp. 223512. 2007 * * *
1/13/2014 15:18:09 * Plasma coati ng and surface modification of amorphous carbon for biomedical applications, Maguire, P. D., Okpalugo, T. I. T. and Ahmad, I. RECENT DEVELOPMENTS IN ADVANCED MATERIALS AND PROCESSES (518), 2006, pp. 477--484. 2006 * * *
1/13/2014 15:18:29 * Tribological, mechanical and electrochemical properties of nanocrystalline copper deposits produced by pulse electrodeposition, Tao, S. and Li, D. NANOTECHNOLOGY (17:1), 2006, pp. 65 - 78. 2006 * * *
1/13/2014 15:17:53 * Preparation and characterization of polypyrrole/TiO2 coaxial nanocables, Lu, X., Zhao, Q., Liu, X., Wang, D., Zhang, W., Wang, C. and Wei, Y. MACROMOLECULAR RAPID COMMUNICATIONS (27:6), 2006, pp. 430 - 434. 2006 * * *
1/13/2014 15:17:41 * In situ measurements of simultaneous electronic behavior of Cu and Al induced by mechanical deformation Li, W. and Li, D. JOURNAL OF APPLIED PHYSICS (99:7), 2006, pp. 073502. 2006 * * *
1/13/2014 15:19:07 * Detection of Metal Fatigue and Defects by Electron Work Function Topography and Gradient Woo, G. H. California State Science Fair - Applied Mechanics/ Structures Mechanisms/ Manufacturing, 2006. 2006 * * *
1/13/2014 15:17:08 * Variation of surface morphology and electronic behavior under dynamic tensile conditions, Li, W., Cai, M ., Zong, Z. and Yu, S. APPLIED PHYSICS LETTERS (88:18), 2006, pp. 181902. 2006 * * *
1/13/2014 15:17:29 * Influence of surface morphology on corrosion and electronic behavior, Li, W. and Li, D. ACTA Materialia (54:2), 2006, pp. 445 - 452. 2006 * * *
1/13/2014 15:19:19 * The electronic and optoelectronic properties study of N,N-dimethylperylene-3,4,9, 10- dicarboximide/ITO film using surface photovoltage technique, Zhang, Q., W ang, D., Wei, X., Zhao, Q., Lin, Y. and Yang, M. MATERIALS CHEMISTRY AND PHYSICS (100:2-3), 2006, pp. 230 - 235. 2006 * * *
1/13/2014 15:16:38 * Direct comparison of photoemission spectroscopy and in situ Kelvin probe work function measurements on indium tin oxide films, Beerbom, M., Lagel, B., Cascio, A., Doran, B. and Schlaf, R. JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA (152:1-2), 2006, pp. 12 - 17. 2006 * * *
1/13/2014 15:21:27 * Electron work function, adhesion, and friction between 3d transition metals under light loads, Li, Y. and Li, D. WEAR (259), 2005, pp. 1432 - 1436. 2005 * * *
1/13/2014 15:22:40 * Corrosion and corrosive wear of annealed, impact-fractured and slow bending-fractured surface layers of AISI 1045 steel in a 3.5% NaCl solution, Yin, S. and Li, D. WEAR (259:1 -6), 2005, pp. 383 - 390. 2005 * * *
1/13/2014 15:21:15 * Frictional hardening and softening of steel 52100 during dry sliding, Li, W., Wang, Y. and Yang, X. TRIBOLOGY LETTERS (18:3), 2005, pp. 353 - 357. 2005 * * *
1/13/2014 15:22:16 * Degradation of organic coatings in a corrosive environment: a study by scanning Kelvin probe and scanning acoustic microscope, Reddy, B. and Sykes, J. PROGRESS I N ORGANIC COATINGS (52:4), 2005, pp. 280 - 287. 2005 * * *
1/13/2014 15:22:28 * Effects of pri or cold work on corrosion and corrosive wear of copper in HNO3 and NaCl solutions, Yin, S. and Li, D. MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING (394:1-2), 2005, pp. 266 - 276. 2005 * * *
1/13/2014 15:20:45 * On the correlation between surface roughness and work function in copper, Li, W. and Li, D. JOURNAL OF CHEMICAL PHYSICS (122:6), 2005, pp. 064708. 2005 * * *
1/13/2014 15:21:02 * An electronic criterion for the intrinsic embrittlement of structural intermetallic compounds, Li, W., Wang, Y., Cai, M. and Wang, C. JOURNAL OF APPLIED PHYSICS (98:8), 2005, pp. 083503. 2005 * * *
1/13/2014 15:20:34 * Characterization of interfacial bonding using a scanning Kelvin probe, Li, W. and Li, D. JOURNAL OF APPLIED PHYSICS (97:1), 2005, pp. 014909. 2005 * * *
1/13/2014 15:22:03 * Mechanical stability, corrosion performance and bioresponse of amorphous diamond-like carbon for medical stents and guidewires, Maguire, P. D., McLaughlin, J. A., Okpalugo, T. I. T., Lemoine, P., Papakonstantinou, P., McAdams, E. T., Needham, M., Ogwu, A. A., Ball, M. and Abbas, G. A. DIAMOND AND RELATED MATERIALS (14:8), 2005, pp. 1277--1288. 2005 * * *
1/13/2014 15:20:22 * Variations of work function and corrosion behaviors of deformed copper surfaces, Li, W. and Li, D. APPLIED SUR FACE SCIENCE (240:1-4), 2005, pp. 388 - 395. 2005 * * *
1/13/2014 15:19:38 * Effect of Surface geometrical configurations induced by microcracks on the electron work function, Li, W. and Li, D. ACTA Materialia (53:14), 2005, pp. 3871 - 3878. 2005 * * *
1/13/2014 15:21:42 * Changes in surface roughness and work function of indium-tin-oxide due to KrF excimer laser irradiation, Lin, Y., Baikie, I., Chou, W., Lin, S., Chang, H., Chen, Y. and Liu, W. JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A (23:5), 2005, pp. 1305 - 1308. 2005 * * *
1/13/2014 15:24:03 * Effect of grain size on the electron work function of Cu and Al, Li, W. and Li, D. SURFACE REVIEW AND LETTERS (11:2), 2004, pp. 173 - 178. 2004 * * *
1/13/2014 15:24:15 * Response of the electron work function to deformation and yielding behavior of copper under different stress states, Li, W., Wang, Y. and Li, D. PHYSICA STATUS SOLIDI A-APPLIED RESEARCH (201:9), 2004, pp. 2005 - 2012. 2004 * * *
1/13/2014 15:23:46 * Effects of elastic and plastic deformations on the electron work function of metals during bending tests, Li, W. and Li, D. PHILOSOPHICAL MAGAZINE (84:35), 2004, pp. 3717 - 3727. 2004 * * *
1/13/2014 15:22:55 * Transparent conducting coatings made by chemical nanotechnology processes, Aegerter, M., Al-Dahoudi, N., Solieman, A., Kavak, H. and Oliveira, P. MOLECULAR CRYSTALS AND LIQUID CRYSTALS (417), 2004, pp. 589 - 598. 2004 * * *
1/13/2014 15:23:19 * Effects of grain size from micro scale to nanoscales on the yield strain of brass under compressive and tensile stresses using a Kelvin probing technique, Li, D., Wang, L. and Li, W. MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING (384:1-2), 2004, pp. 355 - 360. 2004 * * *
1/13/2014 15:23:34 * Determination of the yield locus using a Kelvin probing method, Li, W. and Li, D. JOURNAL OF PHYSICS D-APPLIED PHYSICS (37:6), 2004, pp. 948 - 951. 2004 * * *
1/13/2014 15:24:27 * Experimental studies on relationships between the electron work function, adhesion, and friction for 3d transition metals, Li, Y. and Li, D. JOURNAL OF APPLIED PHYSICS (95:12), 2004, pp. 7961 - 7965. 2004 * * *
1/13/2014 15:25:05 * Breakdown of organic coatings in corrosive environments examined by scanning Kelvin probe and scanning acoustic microscopy, Reddy, B., D oherty, M. and Sykes, J. ELECTROCHIMICA ACTA (49:17-18), 2004, pp. 2965 - 2972. 2004 * * *
1/13/2014 15:24:39 * The effect of silicon doping and thermal annealing on the electrical and structural properties of hydrogenated amorphous carbon thin films, Okpalugo, T. I. T., Maguire, P. D., Ogwu, A. A. and McLaughlin, J. A. D. DIAMOND AND RELATED MATERIALS (13:4-8), 2004, pp. 1549--1552. 2004 * * *
1/13/2014 15:24:51 * Platelet adhesion on silicon modified hydrogenated amorphous carbon films, Okpalugo, T. I. T., Ogwu, A. A., Maguire, P. D. and McLaughlin, J. A. D. BIOMATERIALS (25:2), 2004, pp. 239--245. 2004 * * *
1/13/2014 15:23:07 * Deposition of carbon films onto metal and silicon substrates by filtered cathodic vacuum arc, plasma enhanced CVD and unbalanced magnetron sputtering, Ahmad, I., M aguire, P. D., Lemoine, P., Roy, S. S. and McLaughlin, J. A. DIAMOND AND RELATED MATERIALS (13:4-8), 2004, pp. 1346--1349. 2004 * * *
1/13/2014 15:26:24 * A study on the kinetic response of the electron work function to wear, Li, W. and Li, D. Y. WEAR (255), 2003, pp. 333--340. 2003 * * *
1/13/2014 15:25:41 * Utilisation of a micro-tip scanning Kelvin probe for non-invasive surface potential mapping of mc- Si solar cells, Dirscherl, K., Baikie, I., Forsyth, G. and van der heide, A. SOLAR ENERGY MATERIALS AND SOLAR CELLS (79:4), 2003, pp. 485 - 494. 2003 * * *
1/13/2014 15:26:06 * A simple method for determination of the electron work function of different crystallographic faces of copper, Li, W. and Li, D. Y. PHYSICA STATUS SOLIDI A-APPLIED RESEARCH (196:2), 2003, pp. 390--395. 2003 * * *
1/13/2014 15:25:29 * Variable temperature surface photovoltage imaging of oxide and nitride coated multicrystalline silicon solar cells, Baikie, L. and Forsyth, G. Microscopy Of Semiconducting Materials 2003 (:180), 2003, pp. 519--522. 2003 * * *
1/13/2014 15:25:52 * Surface potential and surface photovoltage of oxide and nitride coated multicrystalline silicon solar cells using a scanning Kelvin probe, Forsyth, G., Baikie, L. and van der Heide, A. Microscopy Of Semiconducting Materials 2003 (:180), 2003, pp. 513--518. 2003 * * *
1/13/2014 15:26:36 * Mechanical, electrochemical and tribological properties of nano-crystalline surface of 304 stainless steel, Wang, X. Y. a nd Li, D. Y. WEAR (255), 2003, pp. 836--845. 2003 * * *
1/13/2014 15:27:17 * Effects of ytt rium on mechanical properties and chemical stability of passive film of aluminide coating on 1045 steel, Wang, X. Y. a nd Li, D. Y. SURFACE AND COATINGS TECHNOLOGY (160:1), 2002, pp. 20--28. 2002 * * *
1/13/2014 15:26:52 * Kelvin probing technique: A promising method for the determination of the yield strain of a solid under different types of stress, Li, D. Y. PHYSICA STATUS SOLIDI A-APPLIED RESEARCH (191:2), 2002, pp. 427--434. 2002 * * *
1/13/2014 15:27:30 * Modification of 27Cr cast iron with alloying yttrium for enhanced resistance to sliding wear in corrosive media, Zhang, T. C. and Li, D. Y. METALLURGICAL AND MATERIALS TRANSACTIONS A (33:7), 2002, pp. 1981--1989. 2002 * * *
1/13/2014 15:27:06 * Effects of dislocation on electron work function of metal surface, Li, W. and Li, D. Y. MATERIALS SCIENCE AND TECHNOLOGY (18:9), 2002, pp. 1057--1060. 2002 * * *
1/13/2014 15:28:58 * Beneficial effects of yttrium on the mechanical failure and chemical stability of the passive film of 304 stainless steel, Wang, X. Y. and Li, D. Y. MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING (315:1-2), 2001, pp. 158--165. 2001 * * *
1/13/2014 15:28:20 * Electrical characteristics of nitrogen incorporated hydrogenated amorphous carbon, Magill, D. P., Ogwu, A. A., McLaughlin, J. A., Maguire, P. D., McCullough, R. W., Voulot, D. and Gillen, D. JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A (19:5), 2001, pp. 2456--2462. 2001 * * *
1/13/2014 15:27:41 * Study of high - and low-work-function surfaces for hyperthermal surface ionization using an absolute Kelvin probe, Baikie, I., Peterman, U., Lagel, B. and Dirscherl, K. JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A (19:4), 2001, pp. 1460 - 1466. 2001 * * *
1/13/2014 15:29:27 * Improvement in the corrosion-erosion resistance of 304 stainless steel with alloyed yttrium, Zhang, T. C. and Li, D. Y. JOURNAL OF MATERIALS SCIENCE (36:14), 2001, pp. 3479--3486. 2001 * * *
1/13/2014 15:28:42 * The insulatin g properties of a-C : H on silicon and metal substrates, Maguire, P. D., Magill, D. P., Ogwu, A. A. and McLaughlin, J. A. DIAMOND AND RELATED MATERIALS (10:2), 2001, pp. 216--223. 2001 * * *
1/13/2014 15:28:01 * Electron work function: A parameter sensitive to the adhesion behavior of crystallographic surfaces, Li, D. Y. and Li, W. APPLIED PHYSICS LETTERS (79:26), 2001, pp. 4337--4338. 2001 * * *
1/13/2014 15:27:50 * Pt-Ru model catalysts for anodic methanol oxidation: Influence of structure and composition on the reactivity, Hoster, H., I wasita, T., Baumgartner, H. and Vielstich, W. PHYSICAL CHEMISTRY CHEMICAL PHYSICS (3:3), 2001, pp. 337 - 346. 2001 * * *
1/13/2014 15:30:29 * Boron surface phase on Si(111): atomic structure and Si overgrowth studied by scanning tunneling microscopy and work function measurement, Stimpel, T., Hoster, H., Schulze, J., Baumgartner, H. and Eisele, I. THIN SOLID FILMS (380:1-2), 2000, pp. 29 - 31. 2000 * * *
1/13/2014 15:30:01 * Work function study of rhenium oxidation using an ultra high vacuum scanning Kelvin probe, Baikie, I., Petermann, U., Speakman, A., Lagel, B., Dirscherl, K. and Estrup, P. JOURNAL OF APPLIED PHYSICS (88:7), 2000, pp. 4371 - 4375. 2000 * * *
1/13/2014 15:30:12 * Kelvin probe and ultraviolet photoemission measurements of indium tin oxide work function: a comparison, Kim, J., Lagel, B., Moons, E., Johansson, N., Baikie, I., Salaneck, W., Friend, R. and Cacialli, F. SYNTHETIC METALS (111), 2000, pp. 311 - 314. 2000 * * *
1/13/2014 15:30:43 * UHV-compatible spectroscopic scanning Kelvin probe for surface analysis, Baikie, I., Petermann, U. a nd Lagel, B. 2000 * * * *
1/13/2014 15:31:32 * A novel dete ction system for defects and chemical contamination in semiconductors based upon the Scanning Kelvin Probe, Lagel, B., Baikie, I. and Petermann, U. SURFACE Science (435), 1999, pp. 622 - 626. 1999 * * *
1/13/2014 15:30:54 * In situ work function study of oxidation and thin film growth on clean surfaces, Baikie, I., Petermann, U. and Lagel, B. SURFACE Science (435), 1999, pp. 249 - 253. 1999 * * *
1/13/2014 15:31:11 * Multitip scanning bio-Kelvin probe, Baikie, I., Sm ith, P., Porterfield, D. and Estrup, P. REVIEW OF SCIENTIFIC INSTRUMENTS (70:3), 1999, pp. 1842 - 1850. 1999 * * *
1/13/2014 15:31:44 * Kelvin probe study of metastable states during initial oxygen adsorption dynamics on Si(111) 7 x 7, Petermann, U., Baikie, I. and Lagel, B. THIN SOLID FILMS (344), 1999, pp. 492 - 494. 1999 * * *
1/13/2014 15:31:56 * Low cost PC based scanning Kelvin probe, Baikie, I. and Estrup, P. REVIEW OF SCIENTIFIC INSTRUMENTS (69:11), 1998, pp. 3902 - 3907. 1998 * * *
1/13/2014 15:32:15 * Combined work function and STM study on growth, alloying and oxidation of epitaxial aluminum films on Ru(0001), Kopatzki, E., Keck, H., Baikie, I., Meyer, J. and Behm, R. SURFACE Science (345:1-2), 1996, pp. L11 - L18. 1996 * * *
1/13/2014 15:32:26 * Preferential island nucleation at the elbows of the Au(111) herringbone reconstruction through place exchange, Meyer, J., Baikie, I., Kopatzki, E. and Behm, R. SURFACE SCIENCE (365:1), 1996, pp. L647 - L651. 1996 * * *
1/13/2014 15:32:38 * NOISE AND THE KELVIN METHOD, Baikie, I., Mackenzie, S., Estrup, P. and Meyer, J. REVIEW OF SCIENTIFIC INSTRUMENTS (62:5), 1991, pp. 1326 - 1332. 1991 * * *
1/13/2014 15:32:48 * ANALYSIS OF STRAY CAPACITANCE IN THE KELVIN METHOD, Baikie, I., Ve nderbosch, E., Meyer, J. and Estrup, P. REVIEW OF SCIENTIFIC INSTRUMENTS (62:3), 1991, pp. 725 - 735. 1991 * * *
1/13/2014 15:33:00 * THERMAL-D ESORPTION FROM COEXISTING PHASES-H/MO (100), Meyer, J., Baikie, I., Lopinski, G., Prybyla, J. and Estrup, P. JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A (8:3), 1990, pp. 2468 - 2473. 1990 * * *
1/13/2014 15:33:14 * AUTOMATIC KELVIN PROBE COMPATIBLE WITH ULTRAHIGH-VACUUM, Baikie, I., Va nderwerf, K., Oerbekke, H., Broeze, J. and Vansilfhout, A. REVIEW OF SCIENTIFIC INSTRUMENTS (60:5), 1989, pp. 930 - 934. 1989 * * *
1/13/2014 15:33:25 * INTEGRATED AUTOMATIC MODULAR MEASURING SYSTEM, Baikie, I., Va nderwerf, K. and Hanekamp, L. REVIEW OF SCIENTIFIC INSTRUMENTS (59:9), 1988, pp. 2075 - 2078. 1988 * * *
1/13/2014 15:06:25 SKP5050 A Novel Method for the Determination of Surface Recombination Velocity through Kelvin Probe Measurements Nicholas Alderman*1,2, Mohd Adib Ibrahim1, Lefteris Danos1‰Û , Martin C. Grossel2 and Tom Markvart1, * 2010 Surface passivation of semiconductor materials is a very important factor in the production of high-efficiency devices such as solar cells. Currently, specialist techniques are available for mapping the recombination lifetime of samples (infrared lifetime mapping, microwave reflectance and photoluminescence imaging) [1-3]. These are usually very specific systems for mapping of the recombination lifetime, whilst others are not commercially available. In this work we present a simple technique for assessing the passivation quality of semiconductor surfaces. The Kelvin probe [4-5] has been shown to be a very powerful and versatile tool, allowing the extraction of data such as diffusion length, surface photovoltage and impurity concentrations. This paper investigates the extraction of the surface recombination velocity (and by assuming a bulk lifetime, the recombination lifetime)from the current-voltage (I-V) type dependence of the sample. By using an X-Y stage, the recombination lifetime can be imaged for entire wafers, instead of obtaining an average value of lifetime similar to that obtained from the Sinton WCT-120 lifetime tool. This is useful in determining where further improvements in the surface passivation can be obtained, by observing problem areas in the passivation layer. The Kelvin probe is a surface-sensitive technique, allowing for accurate, fast and facile monitoring of the surface passivation. Thin-film passivation layers have been widely investigated in the literature, with the first passivation properties reported by Lewis et al [6]. Through changing the alkyl group on the surface, the coverage and recombination lifetime can be changed. This allows us to synthesise samples with a variety of recombination lifetimes, allowing us to test our model for extracting recombination lifetimes from kelvin probe measurements. http://www.pvsat.org.uk/PVSAT-9_Proceedings-FINAL.pdf *