Study of Mechanical, Optoelectronic, and thermoelectric aspects of lithium-based double perovskites Li2AgSbX6 (X=Cl, Br, I) for energy harvesting applications

Inorganic double perovskites appear to be incredible materials for renewable energy purposes, particularly in thermoelectric generators and solar cells. This article systematically examined the stability and various characteristics, including mechanical, thermodynamic, optical, and transport features of Li2AgSbX6 (X=Cl, Br, I), based on density functional theory (DFT) using Wien2k. The finding of formation energy is used to ensure thermodynamic strength and evaluate the tolerance factor for their structural integrity. Mechanical stability is verified by fulfilling the Born criteria involving elastic constants. The directional lattice conductivity and Debye temperature have been assessed using Navier's velocities. The distinctive optoelectronic characteristics have been explored by adjusting the band gap from 1.40 to 0.49 eV through the varying halide ions (from Cl to I). We also examined various optical features such as absorption bands, refraction, light energy dispersion, and optical loss of the investigated materials. Key thermoelectric characteristics, including the Seebeck effect, conductivities, and performance, have been analyzed across temperatures ranging from 200 to 600 K. The high figure of merit and minimal lattice vibration at room temperature make Li2AgSbX6, double perovskites (DPs), promising for thermoelectric applications.