An <i>ab Initio</i> Study of Mechanical and Electronic Properties of Stable Phases of CsXBr₃ (X = Ge, Si) Compounds for Solar Cell Applications

Abstract

Utilising the density functional theory, the mechanical and electrical characteristics of Cesium Germanium Bromide, CsGeBr 3 and Cesium Silicon Bromide CsSiBr 3 compounds were computed. The complicated and unique physical and chemical properties of these materials include the ideal geometric property, a limited electronic band structure, a charge density distribution, and specific van Hove singularities in the electronic density of states. With the use of the quantum espresso code and pseudo-potentials taken from the quantum espresso data repository, we have applied density functional theory. Plane Wave (PW) basis set and Projector Augmented Wave (PAW) pseudo potentials were used to compute the ground state energy. For the exchange correlation, where plane wave basis sets are used to expand the electronic structure wave function, the Generalised Gradient Approximation (GGA) was employed. For the computation of mechanical behaviour, including the bulk modulus and elastic constants with their derivatives, Thermo_pw was used as a post-processing algorithm. The theoretical framework that is being taught gives a thorough understanding of the many qualities and possible uses for solar cells and other opto-electronic devices. Both the cubic (high-temperature) and tetragonal (low-temperature) phases of CsGeBr 3 were discovered to have an appropriate gap for solar cells. The edge-sharing monoclinic phase exhibits a greater distortion of the band structure than the cubic phase, which has a lower total energy and a somewhat bigger electronic gap. Although our estimations are less definite because the matching silicon-based compounds have not yet been created, they nonetheless point to a small gap for cubic CsGeBr 3 of about 0.2 - 0.8 eV.