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Rusu M, Kodalle T, Choubrac L, Barreau N, Kaufmann CA, Schlatmann R, Unold T. Electronic Structure of the CdS/Cu(In,Ga)Se 2 Interface of KF- and RbF-Treated Samples by Kelvin Probe and Photoelectron Yield Spectroscopy. ACS Appl Mater Interfaces 2021; 13:7745-7755. [PMID: 33529003 DOI: 10.1021/acsami.0c20976] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ambient-pressure Kelvin probe and photoelectron yield spectroscopy methods were employed to investigate the impact of the KF and RbF postdeposition treatments (KF-PDT, RbF-PDT) on the electronic features of Cu(In,Ga)Se2 (CIGSe) thin films and the CdS/CIGSe interface in a CdS thickness series that has been sequentially prepared during the chemical bath deposition (CBD) process depending on the deposition time. We observe distinct features correlated to the CBD-CdS growth stages. In particular, we find that after an initial CBD etching stage, the valence band maximum (VBM) of the CIGSe surface is significantly shifted (by 180-620 mV) toward the Fermi level. However, VBM positions at the surface of the CIGSe are still much below the VBM of the CIGSe bulk. The CIGSe surface band gap is found to depend on the type of postdeposition treatment, showing values between 1.46 and 1.58 eV, characteristic for a copper-poor CIGSe surface composition. At the CdS/CIGSe interface, the lowest VBM discontinuity is observed for the RbF-PDT sample. At this interface, a thin layer with a graded band gap is found. We also find that K and Rb act as compensating acceptors in the CdS layer. Detailed energy band diagrams of the CdS/CIGSe heterostructures are proposed.
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Affiliation(s)
- Marin Rusu
- Struktur und Dynamik von Energiematerialien, Helmholtz-Zentrum Berlin für Materialien und Energie, Lise-Meitner Campus, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Tim Kodalle
- PVcomB, Helmholtz-Zentrum Berlin für Materialien und Energie, Schwarzschildstr. 3, 12489 Berlin, Germany
| | - Leo Choubrac
- Struktur und Dynamik von Energiematerialien, Helmholtz-Zentrum Berlin für Materialien und Energie, Lise-Meitner Campus, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Nicolas Barreau
- Université de Nantes, CNRS, Institut des Matériaux Jean Rouxel, IMN, F-44000 Nantes, France
| | - Christian A Kaufmann
- PVcomB, Helmholtz-Zentrum Berlin für Materialien und Energie, Schwarzschildstr. 3, 12489 Berlin, Germany
| | - Rutger Schlatmann
- PVcomB, Helmholtz-Zentrum Berlin für Materialien und Energie, Schwarzschildstr. 3, 12489 Berlin, Germany
| | - Thomas Unold
- Struktur und Dynamik von Energiematerialien, Helmholtz-Zentrum Berlin für Materialien und Energie, Lise-Meitner Campus, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
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2
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He J, Armstrong J, Cong P, Menagen B, Igaher L, Beale AM, Etgar L, Avnir D. Affecting an Ultra-High Work Function of Silver. Angew Chem Int Ed Engl 2020; 59:4698-4704. [PMID: 31923344 DOI: 10.1002/anie.201912293] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 11/21/2019] [Indexed: 11/06/2022]
Abstract
An ultra-high increase in the WF of silver, from 4.26 to 7.42 eV, that is, an increase of up to circa 3.1 eV is reported. This is the highest WF increase on record for metals and is supported by recent computational studies which predict the potential ability to affect an increase of the WF of metals by more than 4 eV. We achieved the ultra-high increase by a new approach: Rather than using the common method of 2D adsorption of polar molecules layers on the metal surface, WF modifying components, l-cysteine and Zn(OH)2 , were incorporated within the metal, resulting in a 3D architecture. Detailed material characterization by a large array of analytical methods was carried out, the combination of which points to a WF enhancement mechanism which is based on directly affecting the charge transfer ability of the metal separately by cysteine and hydrolyzed zinc(II), and synergistically by the combination of the two through the known Zn-cysteine finger redox trap effect.
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Affiliation(s)
- Jin He
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Jeff Armstrong
- ISIS Facility, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire, OX11 0QX, UK
| | - Peixi Cong
- Department of Chemistry, University College of London, Gordon Street, London, WC1H 0AJ, UK.,Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire, OX11 0FA, UK
| | - Barak Menagen
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Lior Igaher
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Andrew M Beale
- Department of Chemistry, University College of London, Gordon Street, London, WC1H 0AJ, UK.,Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire, OX11 0FA, UK
| | - Lioz Etgar
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - David Avnir
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
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Xia Y, Cheng B, Fan J, Yu J, Liu G. Unraveling Photoexcited Charge Transfer Pathway and Process of CdS/Graphene Nanoribbon Composites toward Visible-Light Photocatalytic Hydrogen Evolution. Small 2019; 15:e1902459. [PMID: 31257727 DOI: 10.1002/smll.201902459] [Citation(s) in RCA: 100] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/06/2019] [Indexed: 06/09/2023]
Abstract
Converting solar energy into chemical fuels is increasingly receiving a great deal of attention. In this work, CdS nanoparticles (NPs) are solvothermally anchored onto graphene nanoribbons (GNRs) that are longitudinally unzipped from multiwalled carbon nanotubes. The as-synthesized CdS/GNR nanocomposites with recyclability present GNR content-dependent activity in visible-light-driven hydrogen evolution from water splitting. In a range of 1-10 wt% GNRs, the CdS/GNR composites with 2 wt% GNRs achieves the greatest hydrogen evolution rate of 1.89 mmol h-1 g-1 . The corresponding apparent quantum efficiency is 19.3%, which is ≈3.7 times higher than that of pristine CdS NPs. To elucidate the underlying photocatalytic mechanism, a systematic characterization, including in situ irradiated X-ray photoelectron spectroscopy and Kelvin probe measurements, is performed. In particular, the interfacial charge transfer pathway and process from CdS NPs to GNRs is revealed. This work may open avenues to fabricate GNR-based nanocomposites for solar-to-chemical energy conversion and beyond.
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Affiliation(s)
- Yang Xia
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, P. R. China
| | - Bei Cheng
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, P. R. China
| | - Jiajie Fan
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450001, China
| | - Jiaguo Yu
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, P. R. China
| | - Gang Liu
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
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4
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Zu F, Wolff CM, Ralaiarisoa M, Amsalem P, Neher D, Koch N. Unraveling the Electronic Properties of Lead Halide Perovskites with Surface Photovoltage in Photoemission Studies. ACS Appl Mater Interfaces 2019; 11:21578-21583. [PMID: 31124647 DOI: 10.1021/acsami.9b05293] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The tremendous success of metal-halide perovskites, especially in the field of photovoltaics, has triggered a substantial number of studies in understanding their optoelectronic properties. However, consensus regarding the electronic properties of these perovskites is lacking due to a huge scatter in the reported key parameters, such as work function (Φ) and valence band maximum (VBM) values. Here, we demonstrate that the surface photovoltage (SPV) is a key phenomenon occurring at the perovskite surfaces that feature a non-negligible density of surface states, which is more the rule than an exception for most materials under study. With ultraviolet photoelectron spectroscopy (UPS) and Kelvin probe, we evidence that even minute UV photon fluxes (500 times lower than that used in typical UPS experiments) are sufficient to induce SPV and shift the perovskite Φ and VBM by several 100 meV compared to dark. By combining UV and visible light, we establish flat band conditions (i.e., compensate the surface-state-induced surface band bending) at the surface of four important perovskites, and find that all are p-type in the bulk, despite a pronounced n-type surface character in the dark. The present findings highlight that SPV effects must be considered in all surface studies to fully understand perovskites' photophysical properties.
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Affiliation(s)
- Fengshuo Zu
- Institut für Physik & IRIS Adlershof , Humboldt-Universität zu Berlin , 12489 Berlin , Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , 12489 Berlin , Germany
| | - Christian M Wolff
- Institut für Physik und Astronomie , Universität Potsdam , 14776 Potsdam , Germany
| | - Maryline Ralaiarisoa
- Institut für Physik & IRIS Adlershof , Humboldt-Universität zu Berlin , 12489 Berlin , Germany
| | - Patrick Amsalem
- Institut für Physik & IRIS Adlershof , Humboldt-Universität zu Berlin , 12489 Berlin , Germany
| | - Dieter Neher
- Institut für Physik und Astronomie , Universität Potsdam , 14776 Potsdam , Germany
| | - Norbert Koch
- Institut für Physik & IRIS Adlershof , Humboldt-Universität zu Berlin , 12489 Berlin , Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , 12489 Berlin , Germany
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5
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Wu CH, Krieger W, Rohwerder M. On the robustness of the Kelvin probe based potentiometric hydrogen electrode method and its application in characterizing effective hydrogen activity in metal: 5 wt. % Ni cold-rolled ferritic steel as an example. Sci Technol Adv Mater 2019; 20:1073-1089. [PMID: 31807219 PMCID: PMC6882440 DOI: 10.1080/14686996.2019.1687255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 10/30/2019] [Accepted: 10/30/2019] [Indexed: 05/21/2023]
Abstract
Quantitative detection of hydrogen in metal is important in providing a better basis for fundamental investigations of hydrogen embrittlement and hydrogen-related corrosion phenomena. Thermal desorption spectroscopy (TDS) has long been used in characterizing different hydrogen traps inside materials. However, in TDS measurements, the diffusible hydrogen (hydrogen at interstitial sites and weakly bound hydrogen) is usually not detected. The Davanathan-Starchurski permeation technique can cover this shortage. However, for such experiments, the stability of the palladium at the exit side, i.e. in aqueous solution under high potential polarization is an important issue. Alternatively, a Kelvin probe-based (KP-based) potentiometric method developed a few years ago has shown to allow quantitative determination of hydrogen in metal. This method is based on measuring the hydrogen electrode potential on the Pd-coated surface. The aim of this work is to check the reliability of this method and to demonstrate its potential applications in determining the hydrogen amount distributed in both shallow and deep traps in steel. The results reveal that different crystallographic orientation, grain shapes and grain sizes of the deposited palladium film (in the range of variation in this work) do not cause relevant effects on the KP-based hydrogen detection. It is shown in this work that the time lag and permeation rate derived from the permeation curves obtained by this method show a very good reliability and the calculated hydrogen amount shows a good agreement with TDS results. 5 wt.% Ni ferritic steel is used as a model material in this work.
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Affiliation(s)
- Chun-Hung Wu
- Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
- CONTACT Chun-Hung Wu Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, Düsseldorf 40237, Germany
| | - Waldemar Krieger
- Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
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Beyreuther E, Grafström S, Eng LM. Designing a Robust Kelvin Probe Setup Optimized for Long-Term Surface Photovoltage Acquisition. Sensors (Basel) 2018; 18:s18114068. [PMID: 30469394 PMCID: PMC6264026 DOI: 10.3390/s18114068] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 11/16/2018] [Accepted: 11/17/2018] [Indexed: 11/16/2022]
Abstract
We introduce a robust low-budget Kelvin probe design that is optimized for the long-term acquisition of surface photovoltage (SPV) data, especially developed for highly resistive systems, which exhibit-in contrast to conventional semiconductors-very slow photoinduced charge relaxation processes in the range of hours and days. The device provides convenient optical access to the sample, as well as high mechanical and electrical stability due to off-resonance operation, showing a noise band as narrow as 1 mV. Furthermore, the acquisition of temperature-dependent SPV transients necessary for SPV-based deep-level transient spectroscopy becomes easily possible. The performance of the instrument is demonstrated by recording long-term SPV transients of the ultra-slowly relaxing model oxide strontium titanate (SrTiO 3 ) over 20 h.
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Affiliation(s)
- Elke Beyreuther
- Institut für Angewandte Physik, Technische Universität Dresden, Nöthnitzer Str. 61, 01187 Dresden, Germany.
| | - Stefan Grafström
- Fakultät Physik, Technische Universität Dresden, Haeckelstr. 3, 01069 Dresden, Germany.
| | - Lukas M Eng
- Institut für Angewandte Physik, Technische Universität Dresden, Nöthnitzer Str. 61, 01187 Dresden, Germany.
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7
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Di Maria F, Zanelli A, Liscio A, Kovtun A, Salatelli E, Mazzaro R, Morandi V, Bergamini G, Shaffer A, Rozen S. Poly(3-hexylthiophene) Nanoparticles Containing Thiophene-S,S-dioxide: Tuning of Dimensions, Optical and Redox Properties, and Charge Separation under Illumination. ACS Nano 2017; 11:1991-1999. [PMID: 28152312 DOI: 10.1021/acsnano.6b08176] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We describe the preparation of poly(3-hexylthiophene-S,S-dioxide) nanoparticles using Rozen's reagent, HOF·CH3CN, either on poly(3-hexylthiophene) (P3HT) or on preformed P3HT nanoparticles (P3HT-NPs). In the latter case, core-shell nanoparticles (P3HT@PTDO-NPs) are formed, as confirmed by X-ray photoelectron spectroscopy measurements, indicating the presence of oxygen on the outer shell. The different preparation modalities lead to a fine-tuning of the chemical-physical properties of the nanoparticles. We show that absorption and photoluminescence features, electrochemical properties, size, and stability of colloidal solutions can be finely modulated by controlling the amount of oxygen present. Atomic force microscopy measurements on the nanoparticles obtained by a nanoprecipitation method from preoxidized P3HT (PTDO-NPs) display spherical morphology and dimensions down to 5 nm. Finally, Kelvin probe measurements show that the coexistence of p- and n-type charge carriers in all types of oxygenated nanoparticles makes them capable of generating and separating charge under illumination. Furthermore, in core-shell nanoparticles, the nanosegregation of the two materials, in different regions of the nanoparticles, allows a more efficient charge separation.
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Affiliation(s)
| | | | - Andrea Liscio
- CNR-ISOF , Via P. Gobetti 101, I-40129 Bologna, Italy
- CNR-ISC , Via Fosso del Cavaliere 100, I-00133 Roma, Italy
| | | | - Elisabetta Salatelli
- Department of Industrial Chemistry Toso Montanari, University of Bologna , Viale del Risorgimento 4, I-40136 Bologna, Italy
| | - Raffaello Mazzaro
- Department of Chemistry Giacomo Ciamician, University of Bologna , Via Selmi 2, I-40126 Bologna, Italy
- CNR-IMM , Via P. Gobetti 101, I-40129 Bologna, Italy
| | | | - Giacomo Bergamini
- Department of Chemistry Giacomo Ciamician, University of Bologna , Via Selmi 2, I-40126 Bologna, Italy
| | - Avshalom Shaffer
- School of Chemistry, Tel-Aviv University , 69978 Tel Aviv, Israel
| | - Shlomo Rozen
- School of Chemistry, Tel-Aviv University , 69978 Tel Aviv, Israel
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8
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Kryvchenkova O, Abdullah I, Macdonald JE, Elliott M, Anthopoulos T, Lin YH, Igić P, Kalna K, Cobley RJ. Nondestructive Method for Mapping Metal Contact Diffusion in In2O3 Thin-Film Transistors. ACS Appl Mater Interfaces 2016; 8:25631-25636. [PMID: 27581104 PMCID: PMC5140079 DOI: 10.1021/acsami.6b10332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 09/01/2016] [Indexed: 06/06/2023]
Abstract
The channel width-to-length ratio is an important transistor parameter for integrated circuit design. Contact diffusion into the channel during fabrication or operation alters the channel width and this important parameter. A novel methodology combining atomic force microscopy and scanning Kelvin probe microscopy (SKPM) with self-consistent modeling is developed for the nondestructive detection of contact diffusion on active devices. Scans of the surface potential are modeled using physically based Technology Computer Aided Design (TCAD) simulations when the transistor terminals are grounded and under biased conditions. The simulations also incorporate the tip geometry to investigate its effect on the measurements due to electrostatic tip-sample interactions. The method is particularly useful for semiconductor- and metal-semiconductor interfaces where the potential contrast resulting from dopant diffusion is below that usually detectable with scanning probe microscopy.
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Affiliation(s)
- Olga Kryvchenkova
- Electronic Systems Design Centre, Swansea University, Swansea SA1 8EN, U.K.
| | - Isam Abdullah
- School of Physics and Astronomy, Cardiff
University, The Parade, Cardiff CF24 3AA, U.K.
| | - John Emyr Macdonald
- School of Physics and Astronomy, Cardiff
University, The Parade, Cardiff CF24 3AA, U.K.
| | - Martin Elliott
- School of Physics and Astronomy, Cardiff
University, The Parade, Cardiff CF24 3AA, U.K.
| | - Thomas
D. Anthopoulos
- Department of Physics and Centre for Plastic Electronics,
Blackett Laboratory, Imperial College London, London SW7 2AZ, U.K.
| | - Yen-Hung Lin
- Department of Physics and Centre for Plastic Electronics,
Blackett Laboratory, Imperial College London, London SW7 2AZ, U.K.
| | - Petar Igić
- Electronic Systems Design Centre, Swansea University, Swansea SA1 8EN, U.K.
| | - Karol Kalna
- Electronic Systems Design Centre, Swansea University, Swansea SA1 8EN, U.K.
| | - Richard J. Cobley
- Electronic Systems Design Centre, Swansea University, Swansea SA1 8EN, U.K.
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Lee SY, Kim UJ, Chung J, Nam H, Jeong HY, Han GH, Kim H, Oh HM, Lee H, Kim H, Roh YG, Kim J, Hwang SW, Park Y, Lee YH. Large Work Function Modulation of Monolayer MoS2 by Ambient Gases. ACS Nano 2016; 10:6100-6107. [PMID: 27232340 DOI: 10.1021/acsnano.6b01742] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Although two-dimensional monolayer transition-metal dichalcogenides reveal numerous unique features that are inaccessible in bulk materials, their intrinsic properties are often obscured by environmental effects. Among them, work function, which is the energy required to extract an electron from a material to vacuum, is one critical parameter in electronic/optoelectronic devices. Here, we report a large work function modulation in MoS2 via ambient gases. The work function was measured by an in situ Kelvin probe technique and further confirmed by ultraviolet photoemission spectroscopy and theoretical calculations. A measured work function of 4.04 eV in vacuum was converted to 4.47 eV with O2 exposure, which is comparable with a large variation in graphene. The homojunction diode by partially passivating a transistor reveals an ideal junction with an ideality factor of almost one and perfect electrical reversibility. The estimated depletion width obtained from photocurrent mapping was ∼200 nm, which is much narrower than bulk semiconductors.
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Affiliation(s)
- Si Young Lee
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Un Jeong Kim
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - JaeGwan Chung
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Honggi Nam
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Hye Yun Jeong
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Gang Hee Han
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Hyun Kim
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Hye Min Oh
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Hyangsook Lee
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Hyochul Kim
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Young-Geun Roh
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Jineun Kim
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Sung Woo Hwang
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Yeonsang Park
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), and ‡Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Device Laboratory and ∥AE group, Platform Technology Laboratory, Samsung Advanced Institute of Technology , Suwon 443-803, Republic of Korea
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10
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Barnea-Nehoshtan L, Kirmayer S, Edri E, Hodes G, Cahen D. Surface Photovoltage Spectroscopy Study of Organo-Lead Perovskite Solar Cells. J Phys Chem Lett 2014; 5:2408-13. [PMID: 26277807 DOI: 10.1021/jz501163r] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The field of organo-lead perovskite absorbers for solar cells is developing rapidly, with open-circuit voltage of reported devices already approaching the maximal theoretical voltage. Obtaining such high voltages on spun-cast or evaporated thin films is intriguing and calls for detailed investigation of the source of photovoltage in those devices. We present here a study of the roles of the selective contacts to methylammonium lead iodide chloride (MAPbI3-xClx) using surface photovoltage spectroscopy. By depositing and characterizing each layer at a time, we show that the electron-extracting interface is more than twice as effective as the hole-extracting interface in generating photovoltage, for several combinations of electrode materials. We further observe the existence of an electron-injection related spectral feature at 1.1 eV, which might bear significance for the cell's operation. Our results illustrate the usefulness of SPV spectroscopy in highlighting gaps in cells efficiency and for deepening the understanding of charge injection processes in perovskite-based photovoltaics.
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Affiliation(s)
- Lee Barnea-Nehoshtan
- Department of Materials and Interfaces, Faculty of Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Saar Kirmayer
- Department of Materials and Interfaces, Faculty of Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Eran Edri
- Department of Materials and Interfaces, Faculty of Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Gary Hodes
- Department of Materials and Interfaces, Faculty of Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel
| | - David Cahen
- Department of Materials and Interfaces, Faculty of Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel
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Zhao J, Osterloh FE. Photochemical Charge Separation in Nanocrystal Photocatalyst Films: Insights from Surface Photovoltage Spectroscopy. J Phys Chem Lett 2014; 5:782-786. [PMID: 26274067 DOI: 10.1021/jz500136h] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Photochemical charge generation, separation, and transport at nanocrystal interfaces are central to photoelectrochemical water splitting, a pathway to hydrogen from solar energy. Here, we use surface photovoltage spectroscopy to probe these processes in nanocrystal films of HCa2Nb3O10, a proven photocatalyst. Charge injection from the nanoparticles into the gold support can be observed, as well as oxidation and reduction of methanol and oxygen adsorbates on the nanosheet films. The measured photovoltage depends on the illumination intensity and substrate material, and it varies with illumination time and with film thickness. The proposed model predicts that the photovoltage is limited by the built-in potential of the nanosheet-metal junction, that is, the difference of Fermi energies in the two materials. The ability to measure and understand these light-induced charge separation processes in easy-to-fabricate films will promote the development of nanocrystal applications in photoelectrochemical cells, photovoltaics, and photocatalysts.
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Affiliation(s)
- Jing Zhao
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Frank E Osterloh
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
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12
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Evers S, Senöz C, Rohwerder M. Hydrogen detection in metals: a review and introduction of a Kelvin probe approach. Sci Technol Adv Mater 2013; 14:014201. [PMID: 27877549 PMCID: PMC5090567 DOI: 10.1088/1468-6996/14/1/014201] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 11/27/2012] [Indexed: 05/21/2023]
Abstract
Hydrogen in materials is an important topic for many research fields in materials science. Hence in the past quite a number of different techniques for determining the amount of hydrogen in materials and for measuring hydrogen permeation through them have been developed. Some of these methods have found widespread application. But for many problems the achievable sensitivity is usually not high enough and ready-to-use techniques providing also good spatial resolution, especially in the submicron range, are very limited, and mostly not suitable for widespread application. In this work this situation will be briefly reviewed and a novel scanning probe technique based method introduced.
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13
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Capasso A, Salamandra L, Di Carlo A, Bell JM, Motta N. Low-temperature synthesis of carbon nanotubes on indium tin oxide electrodes for organic solar cells. Beilstein J Nanotechnol 2012; 3:524-532. [PMID: 23019547 PMCID: PMC3458597 DOI: 10.3762/bjnano.3.60] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 07/03/2012] [Indexed: 06/01/2023]
Abstract
The electrical performance of indium tin oxide (ITO) coated glass was improved by including a controlled layer of carbon nanotubes directly on top of the ITO film. Multiwall carbon nanotubes (MWCNTs) were synthesized by chemical vapor deposition, using ultrathin Fe layers as catalyst. The process parameters (temperature, gas flow and duration) were carefully refined to obtain the appropriate size and density of MWCNTs with a minimum decrease of the light harvesting in the cell. When used as anodes for organic solar cells based on poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM), the MWCNT-enhanced electrodes are found to improve the charge-carrier extraction from the photoactive blend, thanks to the additional percolation paths provided by the CNTs. The work function of as-modified ITO surfaces was measured by the Kelvin probe method to be 4.95 eV, resulting in an improved matching to the highest occupied molecular orbital level of the P3HT. This is in turn expected to increase the hole transport and collection at the anode, contributing to the significant increase of current density and open-circuit voltage observed in test cells created with such MWCNT-enhanced electrodes.
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Affiliation(s)
- Andrea Capasso
- School of Chemistry Physics and Mechanical Engineering, Queensland University of Technology, George St, 4000 Brisbane, Australia
| | - Luigi Salamandra
- CHOSE (Centre for Hybrid and Organic Solar Energy), Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy
| | - Aldo Di Carlo
- CHOSE (Centre for Hybrid and Organic Solar Energy), Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy
| | - John Marcus Bell
- School of Chemistry Physics and Mechanical Engineering, Queensland University of Technology, George St, 4000 Brisbane, Australia
| | - Nunzio Motta
- School of Chemistry Physics and Mechanical Engineering, Queensland University of Technology, George St, 4000 Brisbane, Australia
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Moos R, Sahner K, Fleischer M, Guth U, Barsan N, Weimar U. Solid state gas sensor research in Germany - a status report. Sensors (Basel) 2009; 9:4323-65. [PMID: 22408529 DOI: 10.3390/s90604323] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 05/04/2009] [Accepted: 05/26/2009] [Indexed: 11/17/2022]
Abstract
This status report overviews activities of the German gas sensor research community. It highlights recent progress in the field of potentiometric, amperometric, conductometric, impedimetric, and field effect-based gas sensors. It is shown that besides step-by-step improvements of conventional principles, e.g. by the application of novel materials, novel principles turned out to enable new markets. In the field of mixed potential gas sensors, novel materials allow for selective detection of combustion exhaust components. The same goal can be reached by using zeolites for impedimetric gas sensors. Operando spectroscopy is a powerful tool to learn about the mechanisms in n-type and in p-type conductometric sensors and to design knowledge-based improved sensor devices. Novel deposition methods are applied to gain direct access to the material morphology as well as to obtain dense thick metal oxide films without high temperature steps. Since conductometric and impedimetric sensors have the disadvantage that a current has to pass the gas sensitive film, film morphology, electrode materials, and geometrical issues affect the sensor signal. Therefore, one tries to measure directly the Fermi level position either by measuring the gas-dependent Seebeck coefficient at high temperatures or at room temperature by applying a modified miniaturized Kelvin probe method, where surface adsorption-based work function changes drive the drain-source current of a field effect transistor.
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