Abstract
Double perovskite halides are potential materials for the production of renewable energy that could meet the global demands for resolving energy shortage issues. In this study, we systematically investigate the Rb2XGaBr6 (X(sic)Na, K) double perovskites using the full-potential linearized augmented plane wave (FP-LAPW+lo) method of density functional theory. The thermodynamic as well as the structural stabilities of the studied materials have been confirmed from the calculated formation energy and Goldsmith tolerance factor (0.89 and 0.92). On the other hand, the calculated Pugh's ratio shows the ductile mechanical nature of the studied materials. The calculated electronic bandgaps of 2.2 eV/1.90 eV for Rb2Na/KGaBr6 lies is in the visible region, which indicated the potential application of these materials in solar cells. The electronic properties of the two compounds are studied using the electronic density of states and the complex dielectric functions are used to evaluate optical properties. Our calculated results clearly indicate the optimum absorption of light in visible regions which depicts the potential of these materials for opto-electronic devices. The thermoelectric properties of the two Rb2XGaBr6 (X(sic)Na, K) double perovskites are also studied in terms of thermal and electrical conductivity and the Seebeck coefficient.