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work function and Electron Affinity of Semiconductors:Doping Effect and Complication due to Fermi Level Pinning

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Energy & Environmental Materials 2021年第3期4卷 273-276页

作者： Guosheng Shao State Center for International Cooperation on Designer Low-carbon and Environmental Materials Zhengzhou UniversityZhengzhou 450001China School of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450001China Zhengzhou Materials Genome Institute XingyangZhengzhou 450100China

Semiconductors are a major category of functional materials essential to various applications to sustain the modern *** applied materials or devices utilizing semiconductors are enabled by interfaces or junctions,such as solar cells,electronic/photonic devices,environmental sensors,and redox ***,the author provides a critical commentary on photoemission measurement of the work function and,more importantly,the electron affinity of semiconductors essential for energy band diagram of *** effort is made towards addressing complications associated with Fermi level pinning due to surficial states of doped semiconductors.

关键词： band edges electron affinity Fermi pinning ultraviolet photoelectron spectroscopy work function

Increased work function in PEDOT:PSS film under ultraviolet irradiation

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Chinese Physics B 2014年第3期23卷 630-635页

作者：邢英杰钱旻昉郭等柱张耿民 Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics Peking University

An increase of work function （0.3 eV） is achieved by irradiating poly（3,4-ethylenedioxythiophene）：poly（styrene sul- fonate）（PEDOT：PSS） film in vacuum with 254-nm ultraviolet （UV） light. The mechanism for such an improvement is investigated by photoelectron yield spectroscopy, X-ray photo electron energy spectrum, and field emission technique. Sur- face oxidation and composition change are found as the reasons for work function increase. The UV-treated PEDOT：PSS film is used as the hole injection layer in a hole-only device. Hole injection is improved by UV-treated PEDOT：PSS film without baring the enlargement of film resistance. Our result demonstrates that UV treatment is more suitable for modifying the injection barrier than UV ozone exposure.

关键词： poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film work function ul- traviolet hole injection layer

Effect of Gd doping on the magnetism and work function of Fe_(1-x)Gd_x/Fe(001)

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Chinese Physics B 2014年第5期23卷 433-438页

作者：汤可嵚钟克华程燕铭黄志高 College of Physics and Energy Fujian Normal UniversityFujian Provincial Key Laboratory of Quantum Manipulation and New Energy Materials

The magnetism and work function Ф of Fe1-xGdx/Fe （001） films have been investigated using first-principles methods based on the density functional theory. The calculated results reveal that Gd doping on the Fe （001） surface would greatly affect the geometrical structure of the system. The restruction of the surface atoms leads to the transition of magnetic coupling between Gd and Fe atoms from ferromagnetic （FM） for 0.5 ≤x ≤ 0.75 to antiferromagnetic （AFM） for x = 1.0. For Fe1-xGdx/Fe （001）（x = 0.25, 0.5, 0.75, 1.0）, the charge transfer from Gd to Fe leads to a positive dipole formed on the surface, which is responsible for the decrease of the work function. Moreover, it is found that the magnetic moments of Fe and Gd on the surface layer can be strongly influenced by Gd doping. The changes of the work function and magnetism for Fe1-xGdx/Fe （001） can be explained by the electron transfer, the magnetic coupling interaction between Gd and Fe atoms, and the complex surface restruction. Our work strongly suggests that the doping of the metal with a low work function is a promising way for modulating the work function of the magnetic metal gate.

关键词： first-principles method doping magnetism work function

Increasing open circuit voltage by adjusting work function of hole-transporting materials in perovskite solar cells

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Nano Research 2016年第6期9卷 1600-1608页

作者： Weibo Yan Yu Li Senyun Ye Yunlong Li Haixia Rao Zhiwei Liu Shufeng Wang Zuqiang Bian Chunhui Huang State Key Laboratory of Rare Earth Materials Chemistry and Applications College of Chemistry and Molecular Engineering Peking University Beijing 100871 China ing 100871 China

A series of conductive polymers, i.e., poly（3-methylthiophene）（PMT）, poly（thiophene）（PT）, poly（3-bromothiophene）（PBT） and poly（3-chlorothiophene）（PCT）, were prepared via the electrochemical polymerization process. Subse- quently, their application as hole-transporting materials （HTMs） in CHBNI-I3Pb｜3 perovskite solar cells was explored. It was found that rationally increasing the work function of HTMs proves beneficial in improving the open circuit voltage （Voc） of the devices with an ITO/conductive-polymer/CHBNHBPbIg/C60/BCP/Ag structure. In addition, the higher-Voc devices with a higher-work-function HTM exhibited higher recombination resistances. The highest open circuit voltage of 1.04 V was obtained from devices with PCT, with a work function of -5.4 eV, as the hole-transporting layer. Its power conversion efficiency attained a value of approximately 16.5%, with a high fill factor of 0.764, an appreciable open voltage of 1.01 V and a short circuit current density of 21.4 ***-2. This simple, controllable and low-cost manner of preparing HTMs will be beneficial to the production of large-area perovskite solar cells with a hole-transportin~ laver.

关键词： perovskite solar cells electrochemical polymerization hole-transporting materials work function recombination resistance

Lower work function of thermoelectric material by ordered arrays

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Science China Chemistry 2016年第10期59卷 1264-1269页

作者： Gang Liu Zhenjie Xue Guiying Xu Cong Yan Tie Wang Laboratory of Special Ceramics and Powder Metallurgy University of Science and Technology Beijing Beijing 100083 China Beijing National Laboratory for Molecular Sciences Key Laboratory of Analytical Chemistry for Living Biosystems Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China

In this paper, PbTe nanocubes are assembled on Bi_(0.5)Sb_(1.5)Te_3 substrates with both ordered and disordered structures through a straightforward method to form a P-N section. The work function of such semiconductor system is then measured by the ultraviolet photoelectron spectroscopy. This results show that the work function of orderly arrayed PbTe deposition is much lower than the disordered assemblies. Such change of the work function provides the possibility to tune it in a P-N section system. The change of the work function is attributed to the less surface roughness and easier electron escaping in the ordered structures.

关键词： work function PbTe nanocubes Bi0.5Sb1.5Te3 P-N sections

In-situ probing of thermal desorption of vapor molecules on a nanowire via work function variance

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Nano Research 2016年第11期9卷 3334-3345页

作者： Kovur Prashanthi John Eric Hawk Ryan McGee Ravi Gaikwad Thomas Thundat Ingenuity Lab Department of Chemical and Materials Engineering University of Alberta Edmonton AB T6G 2V4 Canada

Nanowire sensors based on variations of their electrical properties show great potential for real-time, in situ monitoring of molecular adsorption and desorption. Although the molecular adsorption-induced change in the electronic work function is very sensitive, it does not have any specificity. However, the temperature dependency of the adsorption-induced work function variation can provide limited selectivity based on the desorption temperature. In this study, we report the in situ probing of molecular desorption by monitoring the work function variations of a single Pt nanowire as a function of temperature. The work function of a clean Pt nanowire shows a significant variation due to vapor adsorption at room temperature. Increasing the temperature of the nanowire results in a variation of the work function due to molecular desorption. Experimentally measured differential work function as a function of temperature shows desorption peaks at 36 and 44 ℃ for methanol and ethanol molecules respectively. Adsorption-induced variation of the Pt nanowire work function was further confirmed using ultraviolet photoelectron spectroscopy before and after exposure to methanol vapor. These results show that the molecular adsorption/desorption-induced variation of the work function and its temperature dependency can be used for developing nanoscale electro-calorimetric sensors.

关键词： Kelvin probe microscopy nanowires thermal desorption work function

Modulating J-V hysteresis of planar perovskite solar cells and mini-modules via work function engineering

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Journal of Energy Chemistry 2023年第10期85卷 19-29,I0003页

作者： Zenghua Wang Bing Cai Deyu Xin Min Zhang Xiaojia Zheng Institute of Chemical Materials China Academy of Engineering PhysicsMianyang 621900SichuanChina

Commercialization of perovskite solar cells(PSCs) requires the development of high-efficiency devices with none current density-voltage(J-V) hysteresis. Here, electron transport layers(ETLs) with gradual change in work function(WF) are successfully fabricated and employed as an ideal model to investigate the energy barriers, charge transfer and recombination kinetics at ETL/perovskite interface. The energy barrier for electron injection existing at ETL/perovskite is directly assessed by surface photovoltage microscopy, and the results demonstrate the tunable barriers have significant impact on the J-V hysteresis and performance of PSCs. By work function engineering of ETL, PSCs exhibit PCEs over 21% with negligible hysteresis. These results provide a critical understanding of the origin reason for hysteresis effect in planar PSCs, and clear reveal that the J-V hysteresis can be effectively suppressed by carefully tuning the interface features in PSCs. By extending this strategy to a modified formamidinium-cesium-rubidium(FA-Cs-Rb) perovskite system, the PCEs are further boosted to 24.18%. Moreover, 5 cm × 5 cm perovskite mini-modules are also fabricated with an impressive efficiency of 20.07%, demonstrating compatibility and effectiveness of our strategy on upscaled devices.

关键词： J-V hysteresis work function Planar perovskite solar cells Energy barriers Charge transfer kinetics Perovskite solar modules

work function Optimization Technology of Indium Tin Oxide Films

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Journal of Harbin Institute of Technology(New Series) 2021年第4期28卷 33-39页

作者： Bo Zhang Zhibo Zhang Xintao Guo Ya’nan Yang Ying Liu Lei Yang Jiaqi Zhu Department of Materials Research AVIC Manufacturing Technology InstituteBeijing 100024China National Key Laboratory of Science and Technology on Advanced Composite in Special Environments Harbin Institute of TechnologyHarbin 150001China Center of Analysis and Measurement Harbin Institute of TechnologyHarbin 150001China

Indium tin oxide(In_(2)O_(3)∶Sn)film is one of the most potential materials in the field of semiconductor ***,untreated In2O3∶Sn film has a low work function which can result in a high energy barrier that hinders the passage of carriers through the interface,thus leading to poor overall performance of directly prepared *** this study,crystalline transparent conductive In_(2)O_(3)∶Sn films were prepared by plasma exposure assisted magnetron sputtering under room *** on multiple testing methods,it can be found that the low temperature crystallization characteristics of In_(2)O_(3)∶Sn film were enhanced and the work function was effectively improved after Ar^(+)plasma *** increase of the work function of In_(2)O_(3)∶Sn film was due to the increment of Sn⁃O bond on the surface brought by the transition from low oxidation state Sn^(2+)to high oxidation state Sn^(4+)under the action of high exposure.

关键词： work function indium tin oxide low temperature crystallization plasma exposure

Correlation of work function and stacking fault energy through Kelvin probe force microscopy and nanohardness in diluteα-magnesium

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Journal of Magnesium and Alloys 2024年第1期12卷 237-250页

作者： Yigit Türe Ali Arslan Kaya Hüseyin Aydin Jiang Peng Servet Turan Eskisehir Technical University Porsuk Vocational SchoolElectronics and Automation DepartmentProgram of MechatronicsEskisehirTurkey Mugla Sitki Kocman University Engineering FacultyMetallurgy and Materials Engineering DepartmentMuglaTurkey Hüseying Aydın TUBITAK MRCTurkey Jiang Peng Chongqing UniversityChina Eskisehir Technical University Engineering FacultyMaterials Science and Engineering DepartmentEskisehirTurkey

Electronic interactions of the Group 2A elements with magnesium have been studied through the dilute solid solutions in binary Mg-Ca,Mg-Sr and Mg-Ba *** investigation incorporated the difference in the‘work function'(ΔWF)measured via Kelvin Probe Force Microscopy(KPFM),as a property directly affected by interatomic bond types,*** electronic structure,nanoindentation measurements,and Stacking Fault Energy values reported in the *** was shown that the nano-hardness of the solid-solutionα-Mg phase changed in the order of Mg-Ca>Mg-Sr>***,it was shown,by also considering the nano-hardness levels,that SFE of a solid-solution is closely correlated with its‘work function'***-hardness measurements on the eutectics andΔWF difference between eutectic phases enabled an assessment of the relative bond strength and the pertinent electronic structures of the eutectics in the three *** withΔWF and at least qualitative verification of those computed SFE values with some experimental measurement techniques were considered important as those computational methods are based on zero Kelvin degree,relatively simple atomic models and a number of *** asserted by this investigation,if the results of measurement techniques can be qualitatively correlated with those of the computational methods,it can be possible to evaluate the electronic structures in alloys,starting from binary systems,going to ternary and then multi-elemental *** investigation has shown that such a qualitative correlation is *** all,the SFE values are not treated as absolute values but rather become essential in comparative investigations when assessing the influences of alloying elements at a fundamental level,that is,free electron density *** study indicated that the principles of‘electronic metallurgy'in developing multi-elemental alloy systems can be followed via practical experimental methods,i.e.ΔWF measurements using KPF

关键词： Mg alloys Dilute alloys work function Stacking fault energy Kelvin probe force microscopy Short range order Miedema Nanoindentation Eutectics