Optical and transport properties of novel X2BAgCl6 (where X = K, Rb, Cs, and B = Sc, Y) double perovskites

•DFT method was employed to study properties of X2BAgCl6 (X = K, Rb, and Cs, B = Sc, Y) HDP’s.•Band strucutre of X2BAgCl6 (X = K, Rb, Cs, and B = Sc, Y) represents the semiconducting nature.•The light absorption coefficients of the spectrum exhibited UV-spectrum in comparison with the K2ScCuCl6 and K2YCuCl6.•The SLME-values calculated using JARVIS (Joint Automated Repository for Various Integrated Simulations).•The findings indicate that these double perovskite materials have considerable promise in optical devices. Double perovskites have been found highly stable and suitable for the renewable applications. Predicitng new materials is essential for the continus supply for novel devices. In this work, new halide double perovskites (HDP) X2BAgCl6 (where X = K, Rb, Cs, and B = Sc, Y) have been predicted for the heat and light conversion devices. The negative formation energies ΔEf calculated describes the thermodynamic stability, which supports the existence of the cubic phase of the HDP’s. The elastic properties of these compounds gives better explaination about the ductile nature, mechanical stability and anisotropic aspects. The band gaps for X2BAgCl6 (where X = K, Rb, Cs, and B = Sc, Y) are 3.60, 4.87, 3.69, 4.87, 3.56, and 4.88 eV respectively. The spectral characteristics exhibited their appropriateness for high frequency devices due to their highest absorption in the UV range in comparison to K2ScCuCl6 and K2YCuCl6. These compounds’ reflectivities are low when examined within the specified energy range as comparison to K2ScCuCl6 and K2YCuCl6. Due to their low reflectivities, they are very transparent to incoming photons, which is compatible with their bandgap in comparison with the K2ScCuCl6 and K2YCuCl6. The SLME (%) versus thickness (µm) were calculated by using JARVIS (Joint Automated Repository for Various Integrated Simulations). The calculated figure of merit ZT values for each compound were 0.42, 0.39, 0.39, 0.40, 0.40, and 0.38, respectively as compared to Cs2ScTICl6. These materials exhibits high potential for the high frequency optical and high temperature thermal conversion applications.