Exploring the Li2CuAlX6 (X = Cl, Br, I) lead-free double perovskites for energy harvesting applications

In the current investigation, we theoretically explored the halide-based double perovskites Li2CuAlX6 (X = Cl, Br, I), focusing on their structural, optoelectronic, and thermoelectric attributes. The computation of tolerance factor and enthalpy of formation confirms the thermodynamically stable cubic configuration of all the studied compositions. The study of the band structure reveals the direct bandgap nature with the reduction of bandgap value from visible to infrared region upon replacement of halogens in the compositions. It also enhances the absorption coefficient, dielectric function, refractive index, and reflectivity of Li2CuAlX6 (X = Cl, Br, I) highlighting their feasibility for solar cell industry. Employing semiclassical transport theory based BoltzTrap code, the temperature-dependent various transport parameters including electronic and thermal conductivities, Seebeck coefficient, and power factor are computed which enlightened the path of these materials for thermoelectric devices suitable to work at room temperature.