Effect of Se dopping on the structural and electronic properties, charge redistribution and efficiency of the Cu_2ZnSnS_4 solar cells

摘要

In this study, we systematically investigated the doping effects of Se in CZTS, the crystal structure, electronic structure, and electron charge redistribution properties of Cu2ZnSn(SxSe(1-x))(4) with different concentrations were calculated using density functional theory. Se doping causes very gentle lattice distortion and induces crystal expansion in all concentrations. The calculated formation energies show that Cu2ZnSn(SxSe1-x)(4) alloys are highly miscible with positive formation energy and it costs additional energy to replace Se with S anions to form the Cu2ZnSn(SxSe1-x)(4). The band gaps of the Cu2ZnSn(SxSe1-x)(4) alloy decrease with the increase of Se content.Our results show that Solar cells based on Cu2ZnSn(SxSe1-x)(4) alloys with high Se concentration can have higher efficiency than those with low Se content. The results can be helpful to determine the optimal alloy composition to achieve high efficiency Cu2ZnSn(SxSe1-x)(4)-based solar cells.