Electronic Structure of Cubic CsSnI₃: A First-Principles Assessment and Implications for Lead-Free Perovskite

Lead-free tin-halide perovskites are promising candidates for optoelectronic applications, motivating a detailed understanding of their electronic structure. This study investigates cubic CsSnI₃ using density functional theory within a semilocal Perdew–Burke–Ernzerhof-type generalized-gradient approximation, implemented in Quantum Espresso. The band structure along X→R→M→Γ→R indicates a direct band gap of approximately 0.5 eV, with both the valence-band maximum and conduction-band minimum located at R. The projected density of states shows predominantly Iodine 5p contributions in the valence-band region and Tin 5s/5p contributions in the conduction-band region, with comparatively little Cs contribution near the Fermi level. Band-edge dispersion suggests potentially favourable charge transport. Overall, the results support the semiconducting character of cubic CsSnI₃ and provide a qualitative electronic-structure basis for its relevance to lead-free optoelectronics.