Screening of ii-iv-v₂ materials for photovoltaic applications based on density functional theory calculations

The relative stability of polymorphs and their electronic structure was investigated for II-IV-V₂ materials by using first-principles density functional theory calculations. Our calculation results show that, for Zn-, Cd-, and Be-containing compounds, nitrides favor the 2H polymorph with AB stacking sequence; however, phosphides, arsenides, and antimonides are more stable in the 3C polymorph with the ABC stacking sequence. The electronic band gap of materials was calculated by using hybrid density functional theory methods, and then materials with an ideal band gap for photovoltaic applications were chosen. The experimental synthesis of the screened materials is reported, except for CdSiSb₂, which was found to be unstable in our calculation. The absorption coefficient of the screened materials, especially ZnGeAs₂, was high enough to make thin-film solar cells. The higher stacking fault energy in ZnGeAs₂ than the others is consistent with the larger formation energy difference between the 2H and 3C polymorphs.