Influence of the ZnS precursor thickness on high efficiency Cu2ZnSn(S,Se)4 thin-film solar cells grown by stacked-sputtering and selenization process

CZTSSe thin-films were deposited by stacked sputtering methods (ZnS/SnS/Cu) and annealed with selenization. We adjusted the thickness of the ZnS precursor layer in CZT precursors. A 337 nm thickness of ZnS precursor was shown an efficiency of up to 9.1%. We investigated the secondary phases by Raman spectroscopy and Kelvin probe force microscopy with depth profiles. The Cu₂SnSe₃, ZnSe, and MoSe₂ secondary phases appeared near the back contact region. The phase distributions of the CZTSSe thin-films are different depending on ZnS precursor thickness with different depths. This phase characterization can describe the influences to the device performance of the CZTSSe thin-film solar cells.