Bismuth doping enhances the stability, safety and efficiency of the double perovskite Cs ₂ AgScBr ₆ : A first-principles journey toward high performance

The double perovskite Cs 2 AgScBr 6 is simulated and the effect of bismuth doping on the physical and transport aspects is studied using first-principles approaches. The materials Cs 2 AgSc[Formula: see text]Bi x Br 6 ([Formula: see text], 0.25 and 0.50) possess space group Fm-3 m (225) i.e., the face-centered cubic symmetry with the values of the lattice parameters 10.83, 10.66 and 10.61 Å, respectively for 0%, 25% and 50% doping concentration of Bi. The compounds are structurally, mechanically and thermodynamically stable as per criteria developed by Goldschmidt and Burn–Haun. The ductile nature with Poisson’s ration [Formula: see text] is observed which is attractive for device applications. The gap energies of the band structures are reduced from the Bi-doping i.e., from 2.72[Formula: see text]eV to 1.55[Formula: see text]eV, however, the nature of band gap changes to indirect when the concentration of Bi increases from 25%. The reduction in band gap leads to enhancement in absorption peaks in the visible range, thereby favoring the solar cell performance. Likewise, the thermoelectric performance is also investigated where it is observed that the Bi-doping significantly modifies it. The values of ZT increase with increasing Bi content and are found to be 0.93, 0.94 and 0.95 for Cs 2 AgSc[Formula: see text]Bi x Br 6 with [Formula: see text], 0.25 and 0.50. In a nutshell, Bi doping effectively increases the efficiency and stability of the double perovskite Cs 2 AgScBr 6 for its usage in optoelectronic and thermoelectric applications and reduces the toxicity.