Study of optoelectronic, thermoelectric, mechanical, and thermodynamic properties of Cs2NaTlX6 (X = Cl, Br, I) for energy harvesting

The inorganic double perovskites are remarkable materials for renewable energy which can be realized through solar cells and thermoelectric generators. Here, we have comprehensively elaborated the stability, mechanical, thermodynamic, optical and transport characteristics. The formation energy is computed to ensure thermodynamic validity and the tolerance factor is assessed for structural existence. The elastic constants satisfied the Born criteria and mechanical stability. Naviera's velocities have been used to study the Debye temperature and directional lattice conductivity. Modifying the band gap from 3.1 to 0.58 eV by halide ions (Cl to I) probes the distinct optoelectronic characteristics. Absorption bands, dispersion of light energy, refraction, and optical loss explain the optical characteristics. In addition, the above thermoelectric factors like conductivities, Seebeck effect, and performance are studied in the temperature range of 100–600 K. Large figure of merit and extremely low lattice vibration at room temperature indicate their significance for thermoelectric devices.