Mapping the Energetics of Defect States in Cu2ZnSnS4 films and the Impact of Sb Doping

Devendra Tiwari; M. V. Yakushev; Tristan Koehler; Mattia Cattelan; Neil A Fox; Robert W. Martin; Reiner Klenk; David J Fermin

doi:10.1021/acsaem.1c03729

Mapping the Energetics of Defect States in Cu2ZnSnS4 films and the Impact of Sb Doping

Devendra Tiwari^*, M. V. Yakushev, Tristan Koehler, Mattia Cattelan, Neil A Fox, Robert W. Martin, Reiner Klenk, David J Fermin^*

^*Corresponding author for this work

Research output: Contribution to journal › Article (Academic Journal) › peer-review

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Abstract

The sub-bandgap levels associated with defect states in Cu2ZnSnS4 (CZTS) thin films are investigated by correlating the temperature dependence of the absorber photoluminescence (PL) with the device admittance spectroscopy. CZTS thin films are prepared by thermolysis of molecular precursors incorporating chloride salts of the cations and thiourea. Na and Sb are introduced as dopants in the precursor layers to assess their impact on Cu/Zn and Sn site disorder, respectively. Systematic analysis of PL spectra as a function of excitation power and temperature show that radiative recombination is dominated by quasi-donor–acceptor pairs (QDAP) with a maximum between 1.03 and 1.18 eV. It is noteworthy that Sb doping leads to a transition from localized to delocalized QDAP. The activation energies obtained associated with QDAP emission closely correlate with the activation energies of the admittance responses in a temperature range between 150 K and room temperature in films with or without added dopants. Admittance data of CZTS films with no added dopants also have a strong contribution from a deeper state associated with Sn disorder. The ensemble of PL and admittance data, in addition to energy-filtered photoemission of electron microscopy (EF-PEEM), shows a detailed picture of the distribution of sub-bandgap states in CZTS and the impact of doping on their energetics and device performance.

Original language	English
Pages (from-to)	3933-3940
Number of pages	8
Journal	ACS Applied Energy Materials
Volume	5
Issue number	4
DOIs	https://doi.org/10.1021/acsaem.1c03729
Publication status	Published - 22 Mar 2022

Bibliographical note

Funding Information:
D.T., M.C., N.F., and D.J.F. acknowledge the UK Engineering and Physical Sciences Research Council (EPSRC) for the financial contribution through the grants EP/L017792/1, EP/V008692/1, and EP/V008676/1 and the strategic equipment grants EP/K035746/1 and EP/M000605/1. D.T. is also thankful to the Royal Society of Chemistry for support through grant E20-9404. M.V.Y. is grateful for research support by the state assignment of Ministry of Science and Higher Education of the Russian Federation (“Spin” No. AAAA-A18-118020290104-2). The authors are indebted for access to the facilities at the Department of Physics, SUPA, Strathclyde University.

Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.

Keywords

Cu2ZnSnS4 films
defect states
photoluminescence
admittance spectroscopy
quasi-donor−acceptor pairs

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Solution-Processed Inorganic Thin-Film Photovoltaic Devices (SolPV)
Fermin, D. J. (Principal Investigator)
1/08/21 → 31/01/25
Project: Research

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title = "Mapping the Energetics of Defect States in Cu2ZnSnS4 films and the Impact of Sb Doping",

abstract = "The sub-bandgap levels associated with defect states in Cu2ZnSnS4 (CZTS) thin films are investigated by correlating the temperature dependence of the absorber photoluminescence (PL) with the device admittance spectroscopy. CZTS thin films are prepared by thermolysis of molecular precursors incorporating chloride salts of the cations and thiourea. Na and Sb are introduced as dopants in the precursor layers to assess their impact on Cu/Zn and Sn site disorder, respectively. Systematic analysis of PL spectra as a function of excitation power and temperature show that radiative recombination is dominated by quasi-donor–acceptor pairs (QDAP) with a maximum between 1.03 and 1.18 eV. It is noteworthy that Sb doping leads to a transition from localized to delocalized QDAP. The activation energies obtained associated with QDAP emission closely correlate with the activation energies of the admittance responses in a temperature range between 150 K and room temperature in films with or without added dopants. Admittance data of CZTS films with no added dopants also have a strong contribution from a deeper state associated with Sn disorder. The ensemble of PL and admittance data, in addition to energy-filtered photoemission of electron microscopy (EF-PEEM), shows a detailed picture of the distribution of sub-bandgap states in CZTS and the impact of doping on their energetics and device performance.",

keywords = "Cu2ZnSnS4 films, defect states, photoluminescence, admittance spectroscopy, quasi-donor−acceptor pairs",

author = "Devendra Tiwari and Yakushev, {M. V.} and Tristan Koehler and Mattia Cattelan and Fox, {Neil A} and Martin, {Robert W.} and Reiner Klenk and Fermin, {David J}",

note = "Funding Information: D.T., M.C., N.F., and D.J.F. acknowledge the UK Engineering and Physical Sciences Research Council (EPSRC) for the financial contribution through the grants EP/L017792/1, EP/V008692/1, and EP/V008676/1 and the strategic equipment grants EP/K035746/1 and EP/M000605/1. D.T. is also thankful to the Royal Society of Chemistry for support through grant E20-9404. M.V.Y. is grateful for research support by the state assignment of Ministry of Science and Higher Education of the Russian Federation (“Spin” No. AAAA-A18-118020290104-2). The authors are indebted for access to the facilities at the Department of Physics, SUPA, Strathclyde University. Publisher Copyright: {\textcopyright} 2022 American Chemical Society. All rights reserved.",

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AU - Yakushev, M. V.

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AU - Cattelan, Mattia

AU - Fox, Neil A

AU - Martin, Robert W.

AU - Klenk, Reiner

AU - Fermin, David J

N1 - Funding Information: D.T., M.C., N.F., and D.J.F. acknowledge the UK Engineering and Physical Sciences Research Council (EPSRC) for the financial contribution through the grants EP/L017792/1, EP/V008692/1, and EP/V008676/1 and the strategic equipment grants EP/K035746/1 and EP/M000605/1. D.T. is also thankful to the Royal Society of Chemistry for support through grant E20-9404. M.V.Y. is grateful for research support by the state assignment of Ministry of Science and Higher Education of the Russian Federation (“Spin” No. AAAA-A18-118020290104-2). The authors are indebted for access to the facilities at the Department of Physics, SUPA, Strathclyde University. Publisher Copyright: © 2022 American Chemical Society. All rights reserved.

PY - 2022/3/22

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N2 - The sub-bandgap levels associated with defect states in Cu2ZnSnS4 (CZTS) thin films are investigated by correlating the temperature dependence of the absorber photoluminescence (PL) with the device admittance spectroscopy. CZTS thin films are prepared by thermolysis of molecular precursors incorporating chloride salts of the cations and thiourea. Na and Sb are introduced as dopants in the precursor layers to assess their impact on Cu/Zn and Sn site disorder, respectively. Systematic analysis of PL spectra as a function of excitation power and temperature show that radiative recombination is dominated by quasi-donor–acceptor pairs (QDAP) with a maximum between 1.03 and 1.18 eV. It is noteworthy that Sb doping leads to a transition from localized to delocalized QDAP. The activation energies obtained associated with QDAP emission closely correlate with the activation energies of the admittance responses in a temperature range between 150 K and room temperature in films with or without added dopants. Admittance data of CZTS films with no added dopants also have a strong contribution from a deeper state associated with Sn disorder. The ensemble of PL and admittance data, in addition to energy-filtered photoemission of electron microscopy (EF-PEEM), shows a detailed picture of the distribution of sub-bandgap states in CZTS and the impact of doping on their energetics and device performance.

AB - The sub-bandgap levels associated with defect states in Cu2ZnSnS4 (CZTS) thin films are investigated by correlating the temperature dependence of the absorber photoluminescence (PL) with the device admittance spectroscopy. CZTS thin films are prepared by thermolysis of molecular precursors incorporating chloride salts of the cations and thiourea. Na and Sb are introduced as dopants in the precursor layers to assess their impact on Cu/Zn and Sn site disorder, respectively. Systematic analysis of PL spectra as a function of excitation power and temperature show that radiative recombination is dominated by quasi-donor–acceptor pairs (QDAP) with a maximum between 1.03 and 1.18 eV. It is noteworthy that Sb doping leads to a transition from localized to delocalized QDAP. The activation energies obtained associated with QDAP emission closely correlate with the activation energies of the admittance responses in a temperature range between 150 K and room temperature in films with or without added dopants. Admittance data of CZTS films with no added dopants also have a strong contribution from a deeper state associated with Sn disorder. The ensemble of PL and admittance data, in addition to energy-filtered photoemission of electron microscopy (EF-PEEM), shows a detailed picture of the distribution of sub-bandgap states in CZTS and the impact of doping on their energetics and device performance.

KW - Cu2ZnSnS4 films

KW - defect states

KW - photoluminescence

KW - admittance spectroscopy

KW - quasi-donor−acceptor pairs

U2 - 10.1021/acsaem.1c03729

DO - 10.1021/acsaem.1c03729

M3 - Article (Academic Journal)

C2 - 35497685

SN - 2574-0962

VL - 5

SP - 3933

EP - 3940

JO - ACS Applied Energy Materials

JF - ACS Applied Energy Materials

IS - 4

ER -

Mapping the Energetics of Defect States in Cu2ZnSnS4 films and the Impact of Sb Doping

Abstract

Bibliographical note

Keywords

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