Defect-driven band gap engineering in double perovskite Rb ₂ LiTcO ₆ : a gateway to optoelectronic, spintronics, and renewable energy devices

The ability to tune the electronic structure of vacancy-based double perovskites makes them highly desirable for use in spintronics and energy storage applications. In this study, we examined Rb 2 LiTcO 6 and the vacancy-based Rb 2 TcO 6 double perovskites. The optimum structural parameters and ground state energy are calculated to check the stability of the structure, which is further checked by the formation energy value and tolerance factor. The ductile nature of double perovskite Rb 2 LiTcO 6 and Rb 2 TcO 6 is observed by the comprehensive study of mechanical properties. The evaluation of the Vickers hardness factor suggests that Rb 2 TcO 6 can withstand pressure-induced disturbance as compared to Rb 2 LiTcO 6 . A direct band gap of 4.81 eV is measured for Rb 2 LiTcO 6 in spin up, and for spin down, the band gap is 2.07 eV. The creation of a vacancy reduces the band gap values and the spin-up band gap measured for Rb 2 TcO 6 is 3.2 eV and 1.99 eV for spin down. The optical parameters are also calculated. The vacancy in Rb 2 TcO 6 enhances the strong polarization in the visible region, which infers the possible use in sustainable energy devices. The thermoelectric properties show high ZT values in the spin-up state, showing the potential of the studied materials for renewable energy applications.