Density functionl theory study of Cs2InAgCl(6-x)Brx (x = 0–3) halide double-perovskites

Abstract

Halide double perovskites have recently received much attention due to their application in optoelectronic devices. Cs2InAgCl6 is an exciting compound with a cubic unit cell, Fm-3m space group, and a direct band gap of about 3 eV. This research studied the effect of Br ion doping instead of Cl with the combination of Cs2InAgCl(6-x)Brx (x values between 0 and 3) using density functional theory (DFT) calculations with GGA approximation and norm-conserving pseudopotentials of PBE type. We found that with an increase in Br concentration, the investigated compounds retain their cubic phase. The compounds' calculated lattice constants and band gaps were about 10.44–10.71 Å and 2.12–0.62 eV, respectively. The accurate band gap values were obtained between 3.16 and 1.68 by HSE06 hybrid functional as exchange-correlation. The calculations of the band structure and density of states indicate the direct electron transition from the valence band to the conduction band at the gamma point of the Brillouin zone of the studied compounds. The studied compounds' optical properties show high absorption in the visible and ultraviolet regions, appropriate optical conductivity, and refractive index.