Computational predictions of physical properties of perovskite CsGeR3 (R = F, Cl, Br, and I) materials for optoelectronic applications

Light control or detection becomes a major problem in the modern era that can be solved by perovskite materials. For this purpose, the physical characteristics of halide perovskite materials CsGeR3 (where R = F, Cl, Br, and I) were investigated by using first principle calculations (CASTEP) and GGA-PBE exchange correlation-functional. Pm3m (221) is the space group of the compounds, which have a cubic structure and five atoms per unit cell. Based on calculations, the band structure of CsGeR3 (R = F, Cl, Br, and I) has a 1.87, 1.62, 0.70, 0.62 eV band gap which shows the semiconductor nature. The density of states (DOS), partial DOS, and band structure graphs in perovskite materials provide unambiguous evidence of their semiconductive properties. According to the mechanical properties, modulus (B, G, E), Poisson's ratios (0.30, 0.17,0.25, and 0.23), Pugh's ratio (2.128, 1.217, 1.694, and 1.540), mechanical index (1.088, 1.040, 1.314, and 1.313), Cauchy pressure (10.495, -3.904, 0.377, and -1.424), and hardness Hv (3.024, 1.922, 2.231, and 2.044) are assessed of CsGeR3 (R = F, Cl, Br, and I), respectively. The optical properties of CsGeR3 have also been examined and evaluated in order to detect the light-matter interaction. The study involves the examination of thermodynamic factors such as compressibility, sound velocity, melting temperature, and Debye temperature. According to the physical properties, studied materials CsGeR3 are suitable for optoelectronic applications.