Preparation and characterization of Cu2ZnSn(S,Se)4 thin film as photovoltaic absorber material for solar cells

Cu2ZnSn(S,Se)4 (CZTSSe) thin films were successfully prepared by selenization and sulfurization of Cu2ZnSnS4 (CZTS) nanocrystals synthesized by a single-step process with a new oleamide-based solution. The structure and properties of the CZTSSe thin films were characterized. The results indicated that the CZTSSe films had formed a single-phase structure at 450 °C, and showed rich Cu, Sn and poor Zn compositions, and the Se element in CZTSSe increased with the increase of the annealing temperature. The films were all p-type, and that annealed at 500 °C owned lower resistivity. In the visible light region, the films had strong optical absorption and the observed band gaps are 1.36 eV and 1.32 eV at 450 °C and 500 °C, respectively.