Theoretical investigation of Rb2AuBiX6 (X=Br, cl, F) double perovskite for thermoelectric and optoelectronic applications

The double perovskites are now being looked at as a possible way to meet the energy needs. Therefore, in this study, the structural, optoelectronic, and thermoelectric properties of Pb-free double-perovskites Rb2AuBiX6 (X = Br, Cl, and F) were investigated using both density functional and classical Boltzmann transport models. The structural stability was estimated by evaluating the formation energy and Goldsmith tolerance factor (tG). The Perdew-Burke-Ernzerhof Generalized Gradient Approximation (PBE-GGA) was utilized to determine the band gaps of Rb2AuBiBr6, Rb2AuBiCl6, and Rb2AuBiF6, resulting in values of 0.17, 0.61, and 1.08 eV, respectively. These band gaps have an indirect nature. These materials exhibited significant light absorption (∼5.105 cm−1) and outstanding reflectivity in the visible region (∼38 %), making them suitable for use in solar cells and optoelectronic devices. The BoltzTraP (BT) algorithm was applied to estimate the transport properties of these materials, such as their electrical conductivity, Seebeck coefficient, and thermal conductivity. The results obtained from the coding analysis indicate that Rb2AuBiCl6 and Rb2AuBiF6 possess noteworthy figure of merit values (varying from 0.33 to 0.66). These findings underscore the potential use of these materials in thermoelectric generators.