Rear interface engineering via a facile oxidation process of Mo back contact for highly efficient CZTSSe thin film solar cells

The kesterite-based Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells (TFSCs) are promising absorber material for next-generation TFSCs technology because they exhibit earth-abundant, non-toxic elements and fa-vorable optoelectronic properties. However, the progress and device performance development in CZTSSe TFSCs were limited because of unstable rear interface characteristics near the absorber/molybdenum (Mo) interface, which causes large open-circuit voltage loss. In this study, we report the rear interface en-gineering of CZTSSe TFSCs to improve device performance by introducing an amorphous thin MoOx in-termediate layer by a facile oxidation process. We observed that (i) an amorphous thin MoOx intermediate layer can effectively control the rear interface properties (i.e., inhibiting the formation of Mo(S,Se)2 inter-facial layers and voids at CZTSSe/Mo interface) and (ii) the improved device performance in CZTSSe TFSCs with oxidation (w-oxidation) is attributed primarily to the dramatically decreased shunt conductance, formation of large-sized grains within CZTSSe absorber layer, and improved rear interface characteristics. This study presents a simple and low-temperature oxidation process for rear interface engineering of highly efficient kesterite CZTSSe-based TFSCs.(c) 2022 Published by Elsevier B.V.