Direct evidence of causality between chemical purity and band-edge potential fluctuations in nanoparticle ink-based Cu2ZnSn(S,Se)4 solar cells

Campbell, Stephen, Qu, Yongtao, Major, Jonathan, Lagarde, Delphine, Labbé, Christophe, Maiello, Pietro, Barrioz, Vincent, Beattie, Neil and Zoppi, Guillaume (2019) Direct evidence of causality between chemical purity and band-edge potential fluctuations in nanoparticle ink-based Cu2ZnSn(S,Se)4 solar cells. Journal of Physics D: Applied Physics, 52 (13). p. 135102. ISSN 0022-3727

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Campbell et al - Direct evidence of causality between chemical purity and band-edge potential fluctuations AAM.pdf - Accepted Version
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Official URL: https://doi.org/10.1088/1361-6463/aafe60

Abstract

Kesterite solar cells based on chalcogenide Cu2ZnSn(S,Se)4 (CZTSSe) are a viable approach to thin film photovoltaics, utilising Earth-abundant, nontoxic elements. CZTSSe films produced from nanoparticle inks offer a cost-effective solution-based method of fabrication. However, improving efficiency in these devices has proved challenging, in part due to the presence of detrimental complex defects within the bulk of the CZTSSe absorber. In this study, the behaviour of nanoparticle-based CZTSSe absorbers and solar cells made from relatively low and high quality grade chemicals is investigated with a view to improving cost-effectiveness of the ink-based fabrication process. Photoluminescence (PL) spectroscopy revealed the presence of similar shallow acceptor plus shallow donor states in both low and high purity precursor absorbers. We demonstrate a relationship between the average depth of energy band-edge potential fluctuations and absorber quality where the higher grade chemical precursor-based absorber outperforms the lower purity version. In addition, the low purity precursor absorber had a higher total defect density resulting in a 10 meV increase in the average electrostatic potential fluctuations. Deep level transient spectroscopy (DLTS) in solar devices indicated the presence of detrimental deep defect states in both types of absorber. Notwithstanding the high purity precursor absorber with lower defect density, the power conversion efficiencies of both types of CZTSSe solar cells were similar (~5%), implying an issue other than defects in the absorber bulk inhibits device performance as evidenced by quantum efficiency analysis and current-voltage measurements.

Item Type: Article
Uncontrolled Keywords: Cu2ZnSn(S,Se)4 (CZTSSe), Thin film solar cells, Photoluminescence (PL), Deep Level Transient Spectroscopy (DLTS), Defects
Subjects: H600 Electronic and Electrical Engineering
J500 Materials Technology not otherwise specified
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Paul Burns
Date Deposited: 09 Jan 2019 12:40
Last Modified: 11 Oct 2019 08:24
URI: http://nrl.northumbria.ac.uk/id/eprint/37520

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