Theoretical study of electronic, optical and thermoelectric properties of double halide perovskite Rb₂AgSbCl₆ doped with F; Ge and Te): <i>ab-initio</i> calculations

Abstract In this research paper, we explore the physical properties of Rb 2 AgSbCl 6 doped by F (Fluorine), Ge (Germanium) and Te (Tellurium), using the Full Potential Linear Augmented Plane Wave method. Structural parameters are calculated using optimization and analysis systems. The compounds Rb 2 AgSbCl 6 , Rb 2 AgSbCl 5.5 F 0.5 , Rb 2 AgSbCl 5.5 Ge 0.5 and Rb 2 AgSbCl 5.5 Te 0.5 exhibited negative formation energies of −1.467 eV, −1.747 eV, −1.447 eV, and −1.413 eV, respectively, indicating thermodynamic stability. Furthermore, their band gaps, calculated using the modified Becke–Johnson potential, were determined to be 2.170 eV, 1.890 eV, 0.130 eV, and 0.639 eV. The electronic band gap can be effectively narrowed by incorporating dopant elements, thereby increasing the ability of the studied compounds to absorb visible light (380–790 nm). Optical properties, such as the dielectric function, refractive index, and absorption coefficients, were examined. Following doping, we observed an absorption coefficient on the order of magnitude exceeding 10 4 cm −1 , which is advantageous for applications in the visible light spectrum. Thermoelectric properties, including electrical and thermal conductivity, Seebeck coefficient, power factor, and figure of merit, are predicted using the BoltzTraP tool, which assesses the performance of compounds for thermoelectric applications.