First-principles approach of novel iodine-based double perovskites Cs2BScI6 (where, B = Na and Rb) compounds

First principles approach is employed to explore the physical aspects of halide double perovskites (HDPs) Cs₂BScI₆ (\({\rm{B}}={\rm{Rb}}\) \({\rm{and}}\) \({\rm{Na}}\)) using the full-potential linearized augmented plane-waves method including local orbitals. The band structures and density of states are investigated using the GGA-PBEsol approximation. In addition, the Tran–Blaha-modified Becke–Johnson (TB-mBJ) potential, spin-orbit coupling (SOC) effects, and Hubbard U correction (LSDA + U) methods were applied to reveal the direct (3.027, 2.854, and 2.281) eV and indirect (2.745, 2.564, and 2.107) eV bandgaps for Cs₂RbScI₆ and Cs₂NaScI₆ respectively. Furthermore, the electron density and Poisson’s ratio confirmed the ionic nature of Cs₂RbScI₆ and Cs₂NaScI₆ compounds correspondingly. Moreover, to assess the potential of Na and Rb-based HDPs for optoelectronic applications, various optical parameters are calculated. Moreover, BoltzTraP2 code was employed to investigate the thermoelectric properties within the temperature range of 200–1000 K. The higher values of the Seebeck coefficient, combined with p-type charge mobility and superior ZT values, indicate their potential in thermoelectric generators and automotive technologies.

Graphical Abstract

The physical properties of halide double perovskites Cs₂BScI₆ (\({\rm{B}}={\rm{Rb}}\) \({\rm{and}}\) \({\rm{Na}}\)) were explore using first principle approach. The GGA-PBEsol approximation were used to investigate the band structures and density of states. In addition, the TB-mBJ potential, spin-orbit coupling effects, and Hubbard U correction (LSDA + U) methods were applied to reveal the direct (3.027, 2.854, and 2.281) eV and indirect (2.745, 2.564, and 2.107) eV bandgaps for Cs₂RbScI₆ and Cs₂NaScI₆, respectively. The higher values of the Seebeck coefficient, combined with p-type charge mobility and superior ZT values, indicate their potential in thermoelectric generators and automotive technologies.