First-principles calculations to investigate electronic, optical, mechanical and thermoelectric properties of lead-free halide double perovskites Na2InBiX6 (X = cl, Br and I) for optoelectronic and thermoelectric applications

Physical parameters such as structural, mechanical, electronic, optical and thermoelectric of lead (Pb) free halide double perovskites (DPs) Na2InBiX6 (X = Cl, Br and I), are investigated using density function theory (DFT). Generalize gradient approximation (GGA) with Perdew Burke Ernzerhof (PBE) exchange correlation functional is used to find stable structural parameters. To calculate correct band gap, electronic band structures and density of states (DOS) are evaluated using both GGA-PBE and a hybrid functional HSE06. The optical and mechanical behavior is also evaluated for the considered materials. From the analysis of optical parameters, it is found that the absorption maximum peaks of the photon energy occurred in the visible and ultra violet (UV) region. The large absorption coefficient and higher dielectric constant made these DPs promising candidates for optoelectronics. The analysis of mechanical parameters revealed that these materials are stable. Thermoelectric parameters i.e. thermoelectric parameters, Seebeck coefficient, figure of merit, power factor, electrical conductivity, carrier's concentration and thermal conductivity are also calculated and discussed.