A DFT investigation on halide double perovskites X2ScTlI6 (X= Rb, Cs) for thermoelectric and optoelectronic applications

The present study conducted by first-principles calculations to explore the physical properties of Rb2ScTlI6 and Cs2ScTlI6 double perovskite compound utilizing the FP-LAPW method within the framework of DFT, as implemented in the WIEN2K software package. The electronic and optical characteristics of double perovskite materials were assessed utilizing the TB-mBJ functional, while the structural properties were analyzed employing the GGA-PBE approximation. Electronic properties demonstrated the semiconducting nature of the materials. Optical properties including the dielectric function, absorption coefficient, and reflectivity were computed, affirming the suitability of the compound for device applications across various spectral regions (infrared, visible, and ultraviolet). Additionally, this research delves into the thermoelectric properties, examining factors such as the ratio of thermal to electrical conductivity, a key metric known as the figure of merit, and the Seebeck coefficient. The study reveals that ZT exhibits higher values at lower temperatures but declines as temperature increases. ZT calculations demonstrate minute variations within 200-800 K and computed parameter values are quite favorable for thermoelectric applications of these materials in the future. Notably, this research contributes novelty by investigating the thermoelectric properties of Rb2ScTlI6 and Cs2ScTlI6 double perovskite, encompassing electrical conductivity, Seebeck coefficient, and the figure of merit.