Physical properties of ternary chloro-perovskites KTCl ₃ (T = Ge, Al) for optoelectronic applications

Abstract This study uses density functional theory to investigate various properties of ternary chloro-perovskites, KTCl 3 (T = Ge or Al). Both compounds have a cubic structure with lattice parameters of 5.159 Å for KAlCl 3 and 5.378 Å for KGeCl 3 . KGeCl 3 has a direct band gap of 1.88 eV, while KAlCl 3 exhibits metallic behavior due to aluminum states crossing the energy level, indicating the material’s ability to conduct electricity. Analysis of the electronic structure shows that the electronic properties of KGeCl 3 are primarily influenced by the interactions of germanium and chlorine orbitals, while those of KAlCl 3 are dominated by aluminum orbitals. Optical properties reveal that these materials exhibit strong absorption and high reflectivity in the ultraviolet and visible light range. These properties suggest potential use in optoelectronic applications. Their mechanical stability is supported by elastic constant analysis, which shows their ductile nature and anisotropic behavior, as indicated by the bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio. Pugh’s ratio values of 2.2711 and 2.5035 for KAlCl 3 and KGeCl 3 , respectively, confirm ductility, while Poisson’s ratio suggests a dominant ionic bonding character. These findings provide significant information on the material’s potential applications.