Exploring the effect of metal substitution on cesium iodide perovskites CsBI3 (B = Si, Ge, Sn) for lead-free optoelectronic applications

The commercialization of optoelectronic technologies relies heavily on lead (Pb) free inorganic perovskites. From this point of view, the effect of substituting the B metal in Pb-free perovskite CsBI3 with Si, Ge, and Sn is studied using density functional theory (DFT). DFT is used to predict structural stability, elastic properties, thermodynamic properties, and electronic characteristics of the present investigated materials. The electronic structure investigation reveals that CsBI3 compounds are direct bandgap semiconductor materials. The results revealed that atomic size and atomic orbital spatial extent are the primary factors determining the bandgap. It is found that substituting B cations in the CsBI3 compounds effectively tunes the electronic structure of perovskite crystals, enabling bandgap modulation. The Ge and Sn containing compounds are found to have a suitable bandgap for optoelectronics applications. This work gives an important theoretical guide for developing environmentally benign, inorganic, Pb-free perovskites.