Density Functional Theory Computation of the Electronic, Elastic, Phonon, X-ray Spectroscopy, and the Optoelectronic Properties of CsXI3 (X: Si, Ge, Sn) Halide Perovskite Materials

Perovskites are a promising candidate for various applications including solar cells, light-emitting diodes, photodetectors, and photocatalyst owing to their exceptional properties. However, their long-term stability remains a critical challenge that hinders their widespread use. In this study, we explore key stability factors pertaining to perovskites by examining the structural, mechanical, phonon, thermodynamic, X-ray and optoelectronic properties of CsXI 3 (X: Si, Ge, Sn) using density functional theory (DFT) method, employing the plane wave self-consistent field (PWscf) code embedded in the Quantum Espresso Simulation Package (QESP). From the results, the investigated materials show a tolerance factor of 0.9846, 1.1096, and 0.9982, and octahedral factor of 0.4223, 0.2621, and 0.4029 for CsGeI 3 , CsSiI 3 , and CsSnI 3 , respectively. It was further discovered that the bulk modulus of each crystal dependent on the boiling point of the[Formula: see text] cation in CsXI 3 were the values obtained, which are 7.86, 19.23, and 22.72 corresponding to CsGeI 3 , CsSiI 3 , and CsSnI 3 , respectively. The band structure results clearly indicate a substantial overlap between the valence band and the conduction band of CsXI 3 (X: Si, Ge, Sn), resulting in a complete absence of a bandgap. This observation strongly suggests that the perovskite compound exhibits metallic properties. This study demonstrates a novel method for obtaining stable perovskites of cesium halide suitable for applications in solid-state electronics.