A Theoretical Study for Investigation of Structural, Optical, Electronic, and Mechanical Properties of Double Perovskites Halide for Solar Cell Application

For the calculation of structural, optical, electronic and mechanical properties of a X2ScTlI6 with X = Cs, Li, Na and K possessing a cubic (2 2 5) structure a density functional theory (DFT) approach has been employed. The Perdew–Burke–Ernzerhof (PBE) approach and alongside generalized gradient approximation (GGA) are employed to investigate the structural, bandgap topologies, density of states and optical parameters of the compounds. High values of optical parameters like absorption (α = 105 cm−1) with direct band gap in semiconductor range of (2.05 eV to 2.42 eV) along with enhanced dielectric functions, refractive index, reflectivity, extinction coefficient, in the spectra of visible and ultraviolet region is observed and total and partial densities of states are also investigated for application in optoelectronic devices such as solar cells. The Pugh's ratio indicates these materials exhibit a nature that is also beneficial for solar cells, especially in applications requiring flexibility and mechanical durability.