Abstract
The double perovskites halides are potential materials for renewable energy to meets the demands of the global energy shortage. The structural and thermodynamic stabilities of studied materials are ensured by the Goldsmith tolerance factor (0.86 and 0.91) and negative formation energy. The Poisson and Pugh's ratios show the ductile behaviour of studied compounds. The electronic band gaps 3.42 eV/2.15 eV for Cs2GeCl/Br-6 and maximum absorption of light in ultraviolet and visible regions increased their potential for solar cells and other optoelectronic applications. The thermoelectric characteristics are analyzed by thermal to electrical conductivity ratio and figure of merit criteria. The studied materials have figure of merit 0.80 and 0.82 for Cs2GeCl6 and Cs2GeBr6 at room temperature.