First-principles calculations to investigate mechanical, thermoelectric and optical performance of inorganic double perovskites Rb₂AgAlZ₆ (Z = Br, I) for energy harvesting

The clean and green energy is a merging technology of advanced era to achieve the demands of energy requirements. For this purpose, the double perovskites Rb₂AgAlZ₆ (Z = Br, I) are explored comprehensively in terms of optical, mechanical, thermoelectric, and thermodynamic characteristics. The stability of structures, elastic and thermodynamic have been ensured through tolerance factor, Born Criteria, and formation energy. The elastic constants of cubic symmetry are analyzed to distinguish ductile/brittle nature, anisotropy, Harness, minimum lattice thermal, conductivity, melting and Debye temperatures. The anions (Br, I) modified the band gaps (2.60, 1.08) eV which turned the absorption of light energy from ultraviolet to visible portion of spectrum. The absorption band of Rb₂AgAsI₆ in the energy range 1.7eV–3.4 eV is particularly significant for solar cells. The large Seebeck coefficient, and electrical conductivity while particularly low lattice thermal conductivity has been increased the figure of merit. The large figure of at low temperature open the new finding roots for realization of these DPs for thermoelectric and other energy applications.