First-principles investigation of double halide perovskite Li2GeSnX6 (X = Cl, Br, I) materials for energy conversion applications

The compositional diversity within halide double perovskites presents significant opportunities for discovering novel materials with exceptional properties applicable across various scientific domains. This study employs first-principles simulations to investigate the structural stability, photoelectric characteristics, thermoelectric performance, and mechanical properties of Li₂GeSnX₆ (X = Cl, Br, I), which are classified as Ge-based halide double perovskites. Using the modified Becke–Johnson potential approach, the band gaps of these double halide materials exhibit 1.81, 1.06, and 0.46 eV, showcasing semiconductor behavior. These materials have maximum absorbance, strong optical conductivity in the visible range, and low reflectivity, indicating that they could be used in solar cells and semiconductor gadgets. Thermoelectric findings affirm the potential of these materials for high-temperature thermoelectric power generation. Additionally, Li₂GeSnCl₆ and Li₂GeSnI₆ display elastic stability, with Cl-based compounds exhibiting ductility and ionic bonding, while I-based counterparts are brittle and demonstrate covalent bonding.