An insight into the optoelectronic, mechanical, thermodynamical, structural and thermoelectric attributes of Cesium based Cs ₂ ZTlI ₆ (Z=K, Rb) for sustainable energy applications

The optoelectronic applications of cesium-based double perovskites are significant because of their tunable band gaps, stability, and eco-friendliness. In this paper, we scrutinized the physical properties of Cs 2 ZTlI 6 ([Formula: see text], Rb) using the FP-LAPW technique. The volume optimization, tolerance factor and ground state energies for Cs 2 ZTlI 6 ([Formula: see text], Rb) are computed to check the structural integrity, meanwhile, the formation energies are computed to ensure thermodynamic stability. The ionic bonding nature is revealed through the electron density contour plots. The elastic constants for Cs 2 ZTlI 6 ([Formula: see text], Rb) are calculated using second-order stress-strain energy equations. The band structure profiles for Cs 2 KTlI 6 and Cs 2 RbTlI 6 depict direct band gaps of 1.07[Formula: see text]eV and 1.22[Formula: see text]eV, respectively. Both Cs 2 KTlI 6 and Cs 2 RbTlI 6 have high polarization in the visible and UV ranges, as evidenced by their optical properties. Their large optical conductivity and considerable polarization throughout these spectra, together with the estimated band gaps, make them ideal for photovoltaic applications. Furthermore, the moderate ZT values and large power factor endorsed their potential as ideal candidates for thermoelectricity.