A luminescence study of Cu2ZnSnSe4/Mo/glass films and solar cells with near stoichiometric copper content

Yakushev, M. V. and Sulimov, M.A. and Márquez-Prieto, J. and Forbes, I. and Edwards, P.R. and Zhivulko, V.D. and Borodavchenko, O.M. and Mudryi, A. V. and Krustok, J. and Martin, R. W. (2019) A luminescence study of Cu2ZnSnSe4/Mo/glass films and solar cells with near stoichiometric copper content. Journal of Physics D: Applied Physics, 52 (5). 055502. ISSN 0022-3727 (https://doi.org/10.1088/1361-6463/aaefe3)

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Abstract

Cu2ZnSnSe4 (CZTSe) is one of the leading candidates for the absorber layer in sustainable solar cells. Thin films of CZTSe with a near stoichiometric [Cu]/[Zn+Sn] were used to produce solar cells with conversion efficiency η = 6.4% by a standard solar cell processing including KCN etching and the deposition of CdS and ZnO. Both CZTSe films and solar cells were examined using photoluminescence (PL) to analyse the nature of radiative recombination and photoluminescence excitation (PLE) at 4.2 K to determine the bandgap (Eg). Low temperature PL spectra of the films reveal an intense band P1 at 0.81 eV and a low intensity band P2 at 0.93 eV. Their temperature and excitation intensity dependencies suggest that they both involve recombinations of free electrons with holes localised at acceptors with the energy level influenced by potential fluctuations in the valence band . We associate P1 and P2 with different fractions of CZTSe: with a lower and higher degree of order of Cu and Zn on the cati on sub-lattice, respectively. Device processing reduced the intensity of P1 by 2.5 whereas the intensity of P2 increased by a 1.5. We assign this to a low temperature annealing due to CdS and ZnO deposition which increased the fraction of CZTSe with high d egree of Cu/Zn order and decreased the fraction with low degree of Cu/Zn order. Device processing increased Eg, blue shifted P1, decreased its width, j-shift and the mean depth of potential fluctuations. These can also be related to the annealing and/or KCN etching and the chemical effect of Cd, due to CdS replacing copper at the CdS - CZTSe interface layer. Processing induced a new broad band P3 at 1.3 eV (quenching with Ea = 200 meV) which we attributed to defects in the CdS layer.

  • Item type:Article
    ID code:66083
    Dates:
    Date
    Event
    30 January 2019
    Published
    28 November 2018
    Published Online
    9 November 2018
    Accepted
    13 September 2018
    Submitted
    Notes:This is an author-created, un-copyedited version of an article accepted for publication in Journal of Physics D: Applied Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://iopscience.iop.org/journal/0022-3727.
    Subjects:Science > Physics
    Department:Faculty of Science > Physics
    Strategic Research Themes > Measurement Science and Enabling Technologies
    Depositing user: Pure Administrator
    Date deposited:13 Nov 2018 11:34
    Last modified:09 Apr 2024 00:24
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/66083
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