Investigating the Physical Characteristics of Halide Double Perovskites X2LiSbI6 (X = K, Cs): A First-Principles Approach

This research presents the structural, dynamic, mechanical, optoelectronic, and thermoelectric (TE) features and energy storage potential of new halide double perovskite (HDPs) X₂LiSbI₆ (X = K, Cs) utilizing the modified Becke-Johnson potential (mBJ) within DFT. The materials’ thermal stability was assessed through thermodynamical factors and formation enthalpy calculations and dynamical stability was confirmed by phonon dispersion curves. The brittle nature of Cs₂LiSbI₆ and ductile nature of K₂LiSbI₆ were validated by analyzing their mechanical properties. The indirect band gaps (E_g) for K₂LiSbI₆ and Cs₂LiSbI₆ calculated using mBJ potential are 2.2 eV and 2.1 eV, correspondingly. Optical features were analyzed to determine the suitability of these halides for photovoltaic devices. The optical absorption α(ω) graph shows largest values at 9.24 and 9.81 eV for Cs₂LiSbI₆ and K₂LiSbI₆, respectively. The BoltzTraP code was utilized to calculate TE properties, which revealed thermal energy conversion mechanisms and efficiency by evaluating thermoelectric characteristics. The TE efficiency parameter (zT) shows maximum values to be 0.73 at 750 K for Cs₂LiSbI₆ and 0.71 at 600 K for K₂LiSbI₆. It indicates their suitability for energy harvesting technologies. Findings show that these HDPs demonstrate significant potential for applications in energy-efficient devices, optoelectronic technologies, and TE systems.