Impact of Cs Substitution on the Optoelectronic Properties of MASnI

The electronic structures and optical characteristics of pristine MASnI3 (MA = CH3NH3) perovskite and cesium (Cs)-substituted MASnI3 were investigated using density functional theory (DFT). The structures were constructed, optimized, and analyzed with the CASTEP code to obtain their band structures and optical properties. This perovskite material is of great interest for next-generation optoelectronic devices. Substituting Cs in MASnI3 perovskite reduces the band gap from 1.051 eV to 0.984 eV and alters the optical response. The incorporation of Cs into the MASnI3 perovskite significantly influences its electronic and optical characteristics, indicating that Cs substitution is a promising strategy for tuning these properties.