Computational Exploration of Innovative Lead-Free DPs X2CdZnCl6 (X = Na and K) DFT Analysis of Optoelectronic, Mechanical and Thermoelectric Performance

Based on DFT computation, the physical properties of newlead-free double perovskites (DPs) X₂CdZnCl₆ (X = Na and K) is carried out within WIEN2K software. The measured formation energy (ΔE_f) and tolerance factor indicate the cubic structure stabilities of investigated materials. The lattice parameters of the compounds Na₂CdZnCl₆ and K₂CdZnCl₆ are equal to 9.98 A° and 10.05 A°, respectively. The examination of the electronic structure through nKTB-mBJ demonstrates that lead free DPs X₂CdZnCl₆ (X = Na and K) exhibit semiconducting behavior with direct bandgap energy. The analysis of optical parameters reveal that the examined compounds have a stronger absorption property in UV region and make them well suited for photovoltaic devices and next-generation technologies. Additionally, using BoltzTrap code, the thermoelectric characteristics are thoroughly examined. The highest Seebeck coefficient values 218.32 and 254.29 µV K⁻¹ for X = Na and K, respectively. According to calculations, the maximum ZT values of 0.7 for Na₂CdZnCl₆ and 0.73 for K₂CdZnCl₆ indicate their potential as promising materials for thermoelectric devices. The acquired figure of merit (ZT) values indictes that examined lead free DPs X₂CdZnCl₆ (X = Na and K) exhibit potential for implementation in thermoelectric devices.