First-Principles Investigation on the Structural and Electronic Properties of Cu₂Zn_1–<i>x</i>In_<i>x</i>SnS₄ Alloys

Cu2ZnSnS4 has attracted significant attention as a promising material for solar cells. However, to the best of our knowledge, the research on utilizing indium reagent for modification remains largely unexplored to date. In this study, first-principles calculations were utilized to systematically investigate the structural and electronic properties of Cu2Zn1–xInxSnS4 (x = 0, 1/8, 1/2, and 1). Our calculations, based on the formation enthalpies, indicate that the crystal structures of Cu2Zn1–xInxSnS4 remain stable upon indium varying concentrations. Furthermore, phonon dispersion analysis shows that increasing indium content shifts the phonon dispersion curves of Cu2Zn1–xInxSnS4 toward imaginary frequencies. In addition, the calculations reveal that the band gap can be effectively tuned. With increasing indium concentrations, the band gap of Cu2ZnSnS4 becomes narrow. Notably, for Cu2Zn1–xInxSnS4 (x = 0, 1/8, and 1/2), all exhibit direct band gaps. The density of states analysis indicates that indium mainly occupies the d-orbitals. These results demonstrate that indium has a substantial impact on the electronic properties. Our findings could be very useful for synthetics of these materials.