Tuning of band gap by anion variation of double perovskites K2AgInX6 (X = Cl, Br) for solar cells and thermoelectric applications

Abstract

In recent research double perovskites have become the burning topic for solar cells because of lead free nature, stability, and exceptional performance. Therefore, here we have explained the optical and transport properties of K2AgInX6 (X ​= ​Cl, Br) for solar cells and thermoelectric generators. The confirmation of thermodynamic stability been reported by formation energy and structural existence by tolerance factor. The band gaps of 2.34 ​eV, 1.37 ​eV, and 0.0 ​eV are computed from the band structures for K2AgInCl6, K2AgInBr6, and K2AgInI6, respectively. The band gap of K2AgInBr6 is found ideal for solar cells having large absorption band (376–612 ​nm) in the visible region. The optical characteristics of K2AgInCl6, and K2AgInBr6 are argued in terms of dielectric constants, refractive index, optical loss, and reflection of light. Finally, the thermoelectric behavior has been described by power factor and figure of merit in terms of carrier's concentration and temperature. The large Seebeck coefficient and remarkably small lattice conductivity increases their significance for thermoelectric generators.