The influence of bandgap tunability on the physical features of Rb2LiSbX6 (X=Cl, Br) double perovskites in the context of green technologies

Abstract

Rubidium-based perovskites have the potential to significantly transform renewable energies by making devices more affordable and environmentally friendly. The DFT is employed to conduct an inclusive analysis of the elastic, structural, electronic structure, transport and optoelectronic properties of Rb2LiSbCl6 and Rb2LiSbBr6. The analysis of tolerance factor, optimization curves and octahedral tilting serves to validate the structural stability. The brittle character of Rb2LiSbCl6 and ductile nature of Rb2LiSbBr6 are substantiated by their mechanical properties. The (W-L) symmetry points for Rb2LiSbCl6 and Rb2LiSbBr6 demonstrate the indirect bandgap of 3.72 eV and 2.9 eV, respectively. A decline in the bandgap is observed upon substitution of the Cl with Br atom. The Kramer-Kronig relations are employed for the assessment of the optical properties, revealing substantial absorption within the UV spectrum for both structures, hence enabling their application in optoelectronics. A wide range of thermoelectric properties are computed utilizing the Boltzmann semi-classical theory. Perovskites possess considerable promise for the implementation of renewable energy applications due to their notable ZT values (i.e., 0.73 for Rb2LiSbCl6 and 0.74 for Rb2LiSbBr6), as well as their enhanced Seebeck coefficients. These characteristics enhance their appropriateness for usage in green technologies.