First-Principles Study on the Structural, Optoelectronic, and Elastic Properties of Halide Perovskites XSnCl₃ (X = Rb, Cs) for Photoelectrode Applications

A DFT study of the XSnCl₃ compounds (X = Rb & CS) was performed using the first principles method to investigate their structural, optical, electrical, and elastic properties using the Perdew-Burke-Ernzerhof (PBE) functional with a Generalized Gradient Approximation (GGA). The results reveal that the investigated band gaps of perovskite are 1.77 eV and 0.956 eV by utilizing the PPE-GGA function. The band structures were also examined by employing the partial density of states (PDOS) and total density of states (TDOS). The calculated part density ofstates and total densities of the states confirmed the degree of electron localization. The obtained lattice parameters were in good agreement with the available experimental and theoretical data. The elastic parameters, such as the anisotropic factor (30.345), bulk modulus RbSnCl₃ are (30.345), RbSnCl₃ (13.292), Pugh’s ratio for RbSnCl₃ (1.54988), and for CsSnCl₃ (− 3.02) and Poisson’s ratio (0.26) were calculated. Elastic property measurements revealed that these compounds exhibited ductility, anisotropy, and mechanical stability. The optical features were comprehensively discussed, including the dielectric function, conductivity, absorption, refractivity, and refractive index in the range of 0–10 eV. The dielectric function has been shown to exhibit a wide range of energy (1.86 and 1.56). It is observed that these materials possess high absorption between the 2 and 5 eV and refractive index (2.12and 2.21), due to which it can be deemed as a suitable candidate for optical lenses and optical coating materials applications.