Insight into electronic and optical properties of inorganic Ge-based halide perovskites (CsGeI₃)

In this chapter, we have investigated the CsGeI3 compound by using first-principle simulations based on the Vienna Ab initio Simulation Package (VASP). The rich physical and chemical properties and orbital hybridizations in the Cs–I and Ge–I bonds are clearly exposed through electronic properties, such as the optimized geometry, the quasi-particle band structure and project-band structure, the density of states and project-density of states, as well as the charge density distributions. In addition, the calculated results of the optical properties are achieved successfully, as the imaginary part and the real part of the dielectric function, the energy loss functions, the absorption coefficients and the reflectivity. Moreover, the electronic properties and optical excitations have connected each other. Consequently, the CsGeI3 compound can be useful for optoelectronic and solar cell applications. Our theoretical study of this compound is motivated to fully understand the diverse phenomena for other perovskite solar cell materials.