Investigation of semiconductor to metallic transitions of perovskite CsGeCl3 material through induced pressure: a DFT calculation for photovoltaic and optoelectronic applications

First-principle investigations explore materials science for functional purposes. The physical properties of CsGeCl₃ are investigated under pressure in steps of 1.0 GPa. The CASTEP and GGA-PBE technique is used to understand the characteristics of cubic-based CsGeCl₃ crystal structures with space group 221. The energy bandgap (BG) exhibited direct semiconductors to metallic transition nature at pressures and its value decreased from 1.06 to 0.0 eV. It is observed during computations that it maintains the cubic phase with lattice parameters decreasing from 5.33 to 5.02 Å. A thorough analysis of optical characteristics under pressure shows that the UV spectrum region corresponds to strong peaks in optical properties, with a slight shift in peaks towards greater energies. Additionally, it satisfies the Born stability for mechanical stability and has an anisotropic (A) nature due to the anisotropic factor (0.529 to 1.501) of unity. The ductile nature of CsGeCl₃ is indicated by the Poisson scale (0.260 to 0.289) limits and Pugh’s ratio (1.751 to 2.037). If Cauchy pressure (C_p) is low, the material shows non-metallic behavior, and at high pressures, it shows metallic behavior, with a range of 1.299 to 9.961 GPa. As a result, the analysis shows that said material is suitable for photovoltaic and optoelectronic activity.