Improvement performance of two-step electrodepositing Cu₂MnSnS₄ thin film solar cells by tuning Cu-Sn alloy layer deposition time

A green and cost-effective two-step electrodeposition process has been used to prepare earth-abundant Cu₂MnSnS₄ (CMTS) thin films. We have systematically studied the influence of tuning the deposition time of Cu-Sn alloy layer from 8 to 15 min on the properties of CMTS thin films and the performance of the solar cells. This process increases the content of Cu and Sn, and the thickness of the final CMTS thin films, and further tunes the band gap from 1.43 to 1.35 eV. Moreover, the amount of MnS secondary phase has been reduced, the crystallinity and morphology of the absorber layers has been significantly improved, and eventually the photovoltaic performance has been remarkably enhanced. Nevertheless, a further increase in the deposition time degrades the crystalline quality of the thin films and forms the Cu₂SnS₃ secondary phase. Particularly, the efficiency of the CMTS thin film solar cells improved nearly tenfold from 0.08% to 0.76% when the Cu-Sn alloy layer deposition time is optimized to 12 min. Notably, this is the highest efficiency for an electrodeposited CMTS solar cell up to now, which offers a promising alternative approach for the preparation of CMTS solar cell devices.