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

Abstract

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 CsXI3 (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 CsGeI3, CsSiI3, and CsSnI3, respectively. It was further discovered that the bulk modulus of each crystal dependent on the boiling point of the[Formula: see text] cation in CsXI3 were the values obtained, which are 7.86, 19.23, and 22.72 corresponding to CsGeI3, CsSiI3, and CsSnI3, respectively. The band structure results clearly indicate a substantial overlap between the valence band and the conduction band of CsXI3 (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.