Opto-electronic and thermoelectric properties of free-lead inorganic double perovskites Rb/Cs2ScAuI6 for energy devices

Nowadays, the search for renewable and sustainable energies is a global concern worldwide. In this regard, extensive studies are devoted to inorganic perovskites; nonetheless, the latter suffers from several drawbacks, such as lead toxicity. In this paper, structural stability, optoelectronics and thermoelectric characteristics of double perovskites (DPs) Rb/Cs2ScAuI6 have been systematically explained. The phonon dispersion is evaluated for structural existence, and the formation energy is determined to confirm thermodynamic stability. In addition, the elastic constants fulfilled the Born stability criteria, and Pugh's ratio (B/G) confirms the ductile nature of studied DPs. The obtained results for electronic characteristics of Rb/Cs2ScAuI6 using mBJ+SOC and HSE06 show that the indirect bandgap nature has bandgap values 1.40/1.95 eV and 1.36/1.90 eV, respectively. Further, optical characteristics of DPs have been investigated in terms of dielectric function up to incident photon energy 0-12 eV. Besides, the transport behavior in terms of temperature, carrier concentration, and chemical potential calculated using the BoltzTrap code indicates that both DPs low thermal conductivity, high electrical conductivity, and high Seebeck coefficient.