Optoelectronic and thermoelectric analysis of halide stable double perovskite Rb2TlSbX6 (X = Cl, Br, I) via DFT calculations

Abstract

To explore a good candidate for solar cell applications as an alternative to lead-independent materials, we calculated the structural and mechanical stability of the Rb2TlSbX6 (X = Cl, Br, I) compounds with PBEsol potential. The optoelectronic and thermoelectric behaviors of these compounds are computed with TB-mBJ potential. Our results indicate that these materials possessed excellent structural, mechanical, and thermal stability on the basic values of their Goldsmith’s, elastic parameters and negative formation energies. The dynamic stability is observed through phonon dispersion curve and found that all materials are dynamically stable. The computed values of Poisson and Pugh ratios and a positive value of Cauchy’s pressure indicate the ductile nature of these materials. We observed the low direct bandgaps for Rb2TlSbCl6, (1.486 eV), Rb2TlSbBr6 (2.07 eV), and Rb2TlSbI6 (1.04 eV) unlike the majority of halide double perovskite family have large bandgap values in literature. In addition, the computed optical and thermoelectric characteristics of the Rb2TlSbX6 (X = Cl, Br, I) materials show large values of absorption and optical conductivity with low reflectivity and energy loss at small energy ranges. According to these findings, all these halogen-based double perovskite materials have the potential to be employed as photovoltaic absorb materials in solar cell applications. Furthermore, the large values of the Seebeck coefficient, high-power factor and figure of merit (ZT) at room temperature also ensured their significance for thermoelectric generators.

Keywords

• Double Perovskites
• WIEN2k
• Optical absorption
• Seebeck coefficient
• Power Factor