Frist principle study of double perovskites Cs2AgSbX6 (X = Cl, Br, I) for solar cell and renewable energy applications

The double perovskites are potential aspirant for clean energy harvesting purposes to cover up the globally shortcomings of energy. Here in the present article, the optoelectronic and thermoelectric characteristics of Cs2AgSbX6 (X = Cl, Br, I) are thoroughly investigated. The dynamic and structural behaviors are determined by tolerance factor, octahedral factor, formation energy and phonon dispersion band structures. It is found the band gaps decreases from 1.94 eV to 1.70 eV, and 0.70 eV by the exchange of Cl with Br and I, respectively. The responsible of reducing band gaps is the p-d hybridization among Ag, Sb, and halogen ions. The first and second absorption peaks are recorded at (344 nm, 400 nm, 620 nm) and (282 nm, 335 nm, 460 nm) for Cs2AgSbCl6, Cs2AgSbBr6 and Cs2AgSbI6, respectively. Therefore, absorption bands shift from ultraviolet to visible and infrared regions. Besides, transport characteristics are evaluated by Boltzmann transport theory. The large Seebeck coefficient, electrical conductivity, and ultralow thermal conductivity enrich the figure of merit at room temperature. Therefore, the studied materials are highly recommended for energy harvesting applications.