A computational insight into Rb2ASbX6 (A=Tl, Cu & X=I, Cl) double perovskites for energy storage and optoelectronic applications

Double perovskites are considered to be outstanding materials for encountering the energy crises faced by the world community. This article comprehensively addresses the electronic structure, mechanical, optical and transport attributes of Rb(2)ASbX(6) (A=Tl, Cu & X=I, Cl) double perovskites by using the DFT approach. The structural and thermodynamic stability is confirmed with negative formation energy and tolerance factor. An indirect bandgap of 1.06 eV for Rb2CuSbCl6 and a direct bandgap of 1.12 eV for Rb2TlSbI6 have been found. Mechanical properties are analyzed through elastic parameters. The absorption is found in visible as well as in ultraviolet regions with the minimum energy loss suggesting their possible use in optoelectronic applications. The thermoelectric ability is judged through the computation of transport parameters. The ZT values of 0.79 for Rb2CuSbCl6 and 0.75 for Rb2TlSbI6 endorsed their potential for renewable devices.