Determination of the light matter interaction and thermal heat conversion efficiency of K ₂ TlAsZ ₆ (Z = F, Cl, Br, and I) using a DFT approach

Double perovskites have garnered significant attention as promising alternatives for sustainable energy solutions owing to their structural versatility and potential for integration into optoelectronic technologies. Halide double perovskites K₂TlAsZ₆ (Z = F, Cl, Br, and I) were systematically studied using density functional theory to assess their potential for optoelectronic and thermoelectric applications. Calculations were performed using the FP-LAPW + lo method, confirming structural and thermodynamic stability <i>via</i> formation energy, and the Goldschmidt's tolerance factor. The electronic structure calculations using the TB-mBJ + SOC potential revealed direct bandgaps ranging from 3.25 eV (Z = F) to 0.37 eV (Z = I), with significant UV absorption observed in the optical spectra. Thermoelectric performance <i>versus</i> chemical potential, evaluated <i>via</i> the Boltzmann transport theory, showed promising <i>ZT</i> values approaching 1.0 at 1000 K. Additionally, negative Gibbs free energy and increasing entropy with temperature indicate good thermal stability. These results suggest that K₂TlAsZ₆ compounds are promising materials for next-generation optoelectronic and thermoelectric devices.