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

Tiwari, Devendra, Yakushev, Michael V., Koehler, Tristan, Cattelan, Mattia, Fox, Neil, Martin, Robert W., Klenk, Reiner and Femin, David J. (2022) Mapping the Energetics of Defect States in Cu2ZnSnS4 films and the Impact of Sb Doping. ACS Applied Energy Materials, 5 (4). pp. 3933-3940. ISSN 2574-0962

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Official URL: https://doi.org/10.1021/acsaem.1c03729

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.

Item Type: Article
Additional Information: Funding information: DT, MC, NF and DJF would like to 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. DT is also thankful to the Royal Society of Chemistry for support through grant E20-9404. MVY is grateful to research support by the state assignment of Ministry of Science and Higher Education of the Russian Federation (“Spin” No. АААА-А18 118020290104-2). The authors are indebted to access to the facilities at the Department of Physics, SUPA, Strathclyde University.
Uncontrolled Keywords: Cu2ZnSnS4 films defect states photoluminescence admittance spectroscopy quasi-donor−acceptor pairs photoemission electron microscopy Sb doping
Subjects: F200 Materials Science
F300 Physics
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: John Coen
Date Deposited: 15 Feb 2022 12:02
Last Modified: 18 May 2022 15:45
URI: http://nrl.northumbria.ac.uk/id/eprint/48469

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