Influence of the selenization condition on the properties of ambient-air processed CZTSSe thin films and device performance

Abstract Thoroughly understanding and well controlling the structure and grain growth of Cu2ZnSn(S,Se)4 (CZTSSe) absorber layer in CZTSSe solar cells are essential for getting high power conversion efficiency. Herein, the Cu2ZnSnS4 (CZTS) precursor films were prepared in ambient-air condition by solution method and the effects of selenization condition on the microstructure and device performance are systematically investigated. It is found the heating-up time determines the formation manner of both top large-grained and middle fine-grained layer, while the substrate affects the growth of bottom large-grained layer. A proper heating-up time could effectively optimize the fine-grained layer and achieve better crystallined CZTSSe absorber layer together with a higher device efficiency of 3.38%. A growth mechanism is suggested for the structure formation of CZTSSe.