Structural, electronic and optical properties of bandgap-tunable Cu 2 ZnSi x Sn 1− x Se 4 alloys

Abstract Density functional theory calculations are performed to investigate the structural, electronic and optical properties of Cu 2 ZnSnSe 4 alloys. The lattice constants linearly decrease with the increment of the Si concentration and the mean atomic weight. The Cu 2 ZnSi x Sn 1−x Se 4 alloys are miscible with low formation enthalpies. A tunable bandgap is obtained in a wide energy range (1.06–2.26 eV) and primarily due to the upward shift of the conduction band minimum. The alloy Cu 2 ZnSi 0.5 Sn 0.5 Se 4 has an optimal bandgap (1.49 eV) and a higher optical absorption coefficient than that of the well-studied CuZnSnS 4 . The bandgap-tunable Cu 2 ZnSi x Sn 1−x Se 4 alloys can be promising for their photovoltaic applications.