First-principle investigations on optoelectronics and thermoelectric properties of lead-free Rb2InSbX6 (X = Cl, Br) double perovskites: for renewable energy applications

In the current study, we analyzed the structural, mechanical, optoelectronics as well as transport characteristics of double perovskite Rb2InSbX6 (X = Cl, Br) employing the FP-LAPW technique executed in WIEN2k. Formation energy, tolerance factor, elastic properties, and phonon dispersion studies demonstrate stability of the investigated compounds. To evaluate the electronic characteristics, PBE-GGA and mBJ potentials were applied. For Rb2InSbX6 (X = Cl, Br), the anticipated band gaps using mBJ are 0.97 eV and 0.54 eV, respectively. The computed elastic constants provided details regarding the material mechanical stability. The investigated compounds are determined to ductile by nature. The optical features are computed within 0-20 eV with regard to real and imaginary dielectric function, reflectivity, and extinction coefficient. The thermoelectric characteristics of the compounds under consideration are computed as temperature varies. The positive value of Seebeck's coefficient (S) reveals p-type nature of carries for cubic Rb2InSbX6 (X = Cl, Br) compounds. The power factor of 4.5 x 10(10) W/K-2 ms and 2.5 x 10(10) W/K-2 ms for Rb2InSbX6 (X = Cl, Br) indicates their applicability in thermoelectric devices. By having strong absorption and outstanding PF, the studied compounds proved their suitability for usage in thermoelectric and photovoltaic applications.