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

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 K₂AgInI_6, 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.