Study of mechanical, optical and transport aspirants of double perovskites Cs2XInI6 (X = Li, Na) for solar cells and clean energy applications

The double perovskites (DPs) are extensively explored materials owing to their potential for optoelectronic and thermoelectric devices. In current report, the density functional theory-based Wien2k code is utilized to check the electrical, mechanical, optical, and thermoelectric characteristics of Cs2XInI6 (X ​= ​Li, Na). The calculation of enthalpy of formation yields information about the thermodynamic stability, while computing the tolerance factor yields information about the structural durability. Elastic constant dependent, moduli of elasticity have been computed which confirm the ductile nature of Cs2LiInI6 and brittle nature of Cs2NaInI6. Utilizing modified Beck and Johnson potential (TB-mBJ) to measure the band structures and optical characteristics reveals the bandgaps of 1.23, and 1.64 ​eV for Li and Na-based DPs, respectively. Additionally, the optical behavior is elaborated by computing refractive index, dielectric constant and reflectivity. The broad absorption bands in visible range increases their potential for solar cells. BoltzTrap code is utilized to compute temperature-dependent transport parameters. The capability of these DPs for thermoelectric applications is determined by figure of merit in the range of 200–800 ​K.