A computational study to explore the effects of copper doping concentration on phase stability, electronic band structure and optical properties of CsSrF3 fluro-perovskite

In this work we have computed the electronic, structural, and optical properties of pure and Cu-doped cubic CsSrF3 in the context of density functional theory (DFT). The optimised lattice parameter for pure material was obtained 4.99 Å which has great correspondence to its reported value that is 4.83 Å. The concentration of copper was varied (from x = 0, 0.03, 0.11, 0.22 0.33) that led to an increase in the lattice constant of doped CsSrF3 from 4.99 to 5.150 Å. The electronic bandgap is analysed by investigating the combination of different densities of states. The bandgap of pure CsSrF3 was obtained at 5.66 eV which was direct in nature. Due to variation in copper concentration, the band gap was reduced from 5.66 to 0.727 eV which was also direct in nature. Cu as a dopant at Cs sites in CsSrF3 not only alters electronic but also affects the optical properties of the pure material. The value of pure dielectric function increased from 2.1 to 2.6 in visible region; simultaneously the value of refractive index was changed from 1.4 to 1.6. Due to low refractive index this fluoride-type material can be used for protective coating and for anti-reflection and optical properties are enhanced in lower energy regime.