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Nagai T, Nishinaga J, Tampo H, Kim S, Hirayama K, Matsunobe T, Chen G, Ide Y, Ishizuka S, Shibata H, Niki S, Terada N. Impacts of KF Post-Deposition Treatment on the Band Alignment of Epitaxial Cu(In,Ga)Se 2 Heterojunctions. ACS APPLIED MATERIALS & INTERFACES 2022; 14:16780-16790. [PMID: 35380044 DOI: 10.1021/acsami.1c21193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
In this study, we investigated band alignments at CdS/epitaxial CuInxGa1-xSe2 (epi-CIGSe) and epi-CIGSe/GaAs heterointerfaces for solar cell applications using ultraviolet, inverse, and X-ray photoemission spectroscopy (UPS, IPES, and XPS) techniques. We clarified the impacts of KF postdeposition treatment (KF-PDT) at the CdS/epi-CIGSe front heterointerfaces. We found that KF-PDT changed the conduction band alignment at the CdS/epi-CIGSe heterointerface from a cliff to flat configuration, attributed to an increase in the electron affinity (EA) and ionization potential (IP) of the epi-CIGSe surface because of a decrease in Cu and Ga contents. Herein, we discuss the correlation between the impacts of KF-PDT and the solar cell performance. Furthermore, we also investigated the band alignment at the epi-CIGSe/GaAs rear heterointerface. Electron barriers were formed at the epi-CIGSe/GaAs interface, suppressing carrier recombination as the back surface field. Contrarily, a hole accumulation layer is formed by the valence band bending, which is like Ohmic contact.
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Affiliation(s)
- Takehiko Nagai
- Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
| | - Jiro Nishinaga
- Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
| | - Hitoshi Tampo
- Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
| | - Shinho Kim
- Institute of Materials Technology, Pusan National University, Busan 46241, Republic of Korea
| | - Kazuhiro Hirayama
- Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan
| | - Tatsuo Matsunobe
- Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan
| | - Guanzhong Chen
- Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan
| | - Yuya Ide
- Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan
| | - Shogo Ishizuka
- Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
| | - Hajime Shibata
- Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
| | - Shigeru Niki
- Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
| | - Norio Terada
- Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan
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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 APPLIED MATERIALS & 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] [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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3
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Mirhosseini H, Kormath Madam Raghupathy R, Sahoo SK, Wiebeler H, Chugh M, Kühne TD. In silico investigation of Cu(In,Ga)Se 2-based solar cells. Phys Chem Chem Phys 2020; 22:26682-26701. [PMID: 33236749 DOI: 10.1039/d0cp04712k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Photovoltaics is one of the most promising and fastest-growing renewable energy technologies. Although the price-performance ratio of solar cells has improved significantly over recent years, further systematic investigations are needed to achieve higher performance and lower cost for future solar cells. In conjunction with experiments, computer simulations are powerful tools to investigate the thermodynamics and kinetics of solar cells. Over the last few years, we have developed and employed advanced computational techniques to gain a better understanding of solar cells based on copper indium gallium selenide (Cu(In,Ga)Se2). Furthermore, we have utilized state-of-the-art data-driven science and machine learning for the development of photovoltaic materials. In this Perspective, we review our results along with a survey of the field.
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Affiliation(s)
- Hossein Mirhosseini
- Dynamics of Condensed Matter and Center for Sustainable Systems Design, Chair of Theoretical Chemistry, University of Paderborn, Warburger Str. 100, 33098 Paderborn, Germany.
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Lee H, Jang Y, Nam SW, Jung C, Choi PP, Gwak J, Yun JH, Kim K, Shin B. Passivation of Deep-Level Defects by Cesium Fluoride Post-Deposition Treatment for Improved Device Performance of Cu(In,Ga)Se 2 Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2019; 11:35653-35660. [PMID: 31525944 DOI: 10.1021/acsami.9b08316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Heavy-alkali post-deposition treatments (PDTs) utilizing Cs or Rb has become an indispensable step in producing high-performance Cu(In,Ga)Se2 (CIGS) solar cells. However, full understanding of the mechanism behind the improvements of device performance by heavy-alkali treatments, particularly in terms of potential modification of defect characteristics, has not been reached yet. Here, we present an extensive study on the effects of CsF-PDT on material properties of CIGS absorbers and the performance of the final solar devices. Incorporation of an optimized concentration of Cs into CIGS resulted in a significant improvement of the device efficiency from 15.9 to 18.4% mainly due to an increase in the open-circuit voltage by 50 mV. Strong segregation of Cs at the front and rear interfaces as well as along grain boundaries of CIGS was observed via high-resolution chemical analysis such as atomic probe tomography. The study of defect chemistry using photoluminescence and capacitance-based measurements revealed that both deep-level donor-like defects such as VSe and InCu and deep-level acceptor-like defects such as VIn or CuIn are passivated by CsF-PDT, which contribute to an increased hole concentration. Additionally, it was found that CsF-PDT induces a slight change in the energetics of VCu, the most dominant point defect that is responsible for the p-type conductivity of CIGS.
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Affiliation(s)
- Hojin Lee
- Department of Materials Science and Engineering , Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141 , Republic of Korea
| | - Yuseong Jang
- Department of Materials Science and Engineering , Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141 , Republic of Korea
| | - Sung-Wook Nam
- Department of Molecular Medicine, School of Medicine , Kyungpook National University , Daegu 41404 , Republic of Korea
| | - Chanwon Jung
- Department of Materials Science and Engineering , Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141 , Republic of Korea
| | - Pyuck-Pa Choi
- Department of Materials Science and Engineering , Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141 , Republic of Korea
| | - Jihye Gwak
- Photovoltaic Laboratory , Korea Institute of Energy Research , Daejeon 34129 , Republic of Korea
| | - Jae Ho Yun
- Photovoltaic Laboratory , Korea Institute of Energy Research , Daejeon 34129 , Republic of Korea
| | - Kihwan Kim
- Photovoltaic Laboratory , Korea Institute of Energy Research , Daejeon 34129 , Republic of Korea
| | - Byungha Shin
- Department of Materials Science and Engineering , Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141 , Republic of Korea
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5
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Nicoara N, Manaligod R, Jackson P, Hariskos D, Witte W, Sozzi G, Menozzi R, Sadewasser S. Direct evidence for grain boundary passivation in Cu(In,Ga)Se 2 solar cells through alkali-fluoride post-deposition treatments. Nat Commun 2019; 10:3980. [PMID: 31484943 PMCID: PMC6726603 DOI: 10.1038/s41467-019-11996-y] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 08/16/2019] [Indexed: 11/12/2022] Open
Abstract
The properties and performance of polycrystalline materials depend critically on the properties of their grain boundaries. Polycrystalline photovoltaic materials – e.g. hybrid halide perovskites, copper indium gallium diselenide (CIGSe) and cadmium telluride – have already demonstrated high efficiencies and promise cost-effective electricity supply. For CIGSe-based solar cells, an efficiency above 23% has recently been achieved using an alkali-fluoride post-deposition treatment; however, its full impact and functional principle are not yet fully understood. Here, we show direct evidence for the passivation of grain boundaries in CIGSe treated with three different alkali-fluorides through a detailed study of the nanoscale optoelectronic properties. We determine a correlation of the surface potential change at grain boundaries with the open-circuit voltage, which is supported by numerical simulations. Our results suggest that heavier alkali elements might lead to better passivation by reducing the density of charged defects and increasing the formation of secondary phases at grain boundaries. Grain boundaries play critical roles in determining the properties and performance of solar cells based on polycrystalline materials. Here Nicoara et al. showcase that proper treatments passivate defects at grain boundaries by forming secondary material phases with the CIGSe absorbers and lead to higher Voc.
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Affiliation(s)
- Nicoleta Nicoara
- International Iberian Nanotechnology Laboratory (INL), Av. Mestre José Veiga s/n, 4715-330, Braga, Portugal
| | - Roby Manaligod
- International Iberian Nanotechnology Laboratory (INL), Av. Mestre José Veiga s/n, 4715-330, Braga, Portugal
| | - Philip Jackson
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Meitnerstr. 1, 70563, Stuttgart, Germany
| | - Dimitrios Hariskos
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Meitnerstr. 1, 70563, Stuttgart, Germany
| | - Wolfram Witte
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Meitnerstr. 1, 70563, Stuttgart, Germany
| | - Giovanna Sozzi
- Department of Engineering and Architecture, University of Parma, Parco Area delle Scienze 181A, 43124, Parma, Italy
| | - Roberto Menozzi
- Department of Engineering and Architecture, University of Parma, Parco Area delle Scienze 181A, 43124, Parma, Italy
| | - Sascha Sadewasser
- International Iberian Nanotechnology Laboratory (INL), Av. Mestre José Veiga s/n, 4715-330, Braga, Portugal.
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Kreikemeyer-Lorenzo D, Hauschild D, Jackson P, Friedlmeier TM, Hariskos D, Blum M, Yang W, Reinert F, Powalla M, Heske C, Weinhardt L. Rubidium Fluoride Post-Deposition Treatment: Impact on the Chemical Structure of the Cu(In,Ga)Se 2 Surface and CdS/Cu(In,Ga)Se 2 Interface in Thin-Film Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2018; 10:37602-37608. [PMID: 30272438 DOI: 10.1021/acsami.8b10005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We present a detailed characterization of the chemical structure of the Cu(In,Ga)Se2 thin-film surface and the CdS/Cu(In,Ga)Se2 interface, both with and without a RbF post-deposition treatment (RbF-PDT). For this purpose, X-ray photoelectron and Auger electron spectroscopy, as well as synchrotron-based soft X-ray emission spectroscopy have been employed. Although some similarities with the reported impacts of light-element alkali PDT (i.e., NaF- and KF-PDT) are found, we observe some distinct differences, which might be the reason for the further improved conversion efficiency with heavy-element alkali PDT. In particular, we find that the RbF-PDT reduces, but not fully removes, the copper content at the absorber surface and does not induce a significant change in the Ga/(Ga + In) ratio. Additionally, we observe an increased amount of indium and gallium oxides at the surface of the treated absorber. These oxides are partly (in the case of indium) and completely (in the case of gallium) removed from the CdS/Cu(In,Ga)Se2 interface by the chemical bath deposition of the CdS buffer.
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Affiliation(s)
- Dagmar Kreikemeyer-Lorenzo
- Institute for Photon Science and Synchrotron Radiation (IPS) , Karlsruhe Institute of Technology (KIT) , Hermann-v.-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany
| | - Dirk Hauschild
- Institute for Photon Science and Synchrotron Radiation (IPS) , Karlsruhe Institute of Technology (KIT) , Hermann-v.-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany
- Institute for Chemical Technology and Polymer Chemistry (ITCP) , Karlsruhe Institute of Technology (KIT) , Engesserstr. 18/20 , 76128 Karlsruhe , Germany
- Experimental Physics VII , University of Würzburg , Am Hubland , 97074 Würzburg , Germany
| | - Philip Jackson
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW) , Meitnerstrasse 1 , 70563 Stuttgart , Germany
| | - Theresa M Friedlmeier
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW) , Meitnerstrasse 1 , 70563 Stuttgart , Germany
| | - Dimitrios Hariskos
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW) , Meitnerstrasse 1 , 70563 Stuttgart , Germany
| | - Monika Blum
- Advanced Light Source (ALS) , Lawrence Berkeley National Laboratory , One Cyclotron Road , Berkeley , 94720 California , United States
- Department of Chemistry and Biochemistry , University of Nevada, Las Vegas (UNLV) , 4505 Maryland Parkway , Las Vegas , 89154-4003 Nevada , United States
| | - Wanli Yang
- Advanced Light Source (ALS) , Lawrence Berkeley National Laboratory , One Cyclotron Road , Berkeley , 94720 California , United States
| | - Friedrich Reinert
- Experimental Physics VII , University of Würzburg , Am Hubland , 97074 Würzburg , Germany
| | - Michael Powalla
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW) , Meitnerstrasse 1 , 70563 Stuttgart , Germany
| | - Clemens Heske
- Institute for Photon Science and Synchrotron Radiation (IPS) , Karlsruhe Institute of Technology (KIT) , Hermann-v.-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany
- Institute for Chemical Technology and Polymer Chemistry (ITCP) , Karlsruhe Institute of Technology (KIT) , Engesserstr. 18/20 , 76128 Karlsruhe , Germany
- Department of Chemistry and Biochemistry , University of Nevada, Las Vegas (UNLV) , 4505 Maryland Parkway , Las Vegas , 89154-4003 Nevada , United States
| | - Lothar Weinhardt
- Institute for Photon Science and Synchrotron Radiation (IPS) , Karlsruhe Institute of Technology (KIT) , Hermann-v.-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany
- Institute for Chemical Technology and Polymer Chemistry (ITCP) , Karlsruhe Institute of Technology (KIT) , Engesserstr. 18/20 , 76128 Karlsruhe , Germany
- Department of Chemistry and Biochemistry , University of Nevada, Las Vegas (UNLV) , 4505 Maryland Parkway , Las Vegas , 89154-4003 Nevada , United States
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