First principles elaboration of optoelectronic response, thermoelectric performance, and elastic features of stable and eco-friendly double perovskites K2CuAl(Cl/Br/I)6 for energy applications

Abstract

Here, the investigation of halides double perovskites (HDPs) K2CuAl(Cl/Br/I)6 as a prospective remedy to meet the energy demands has been comprehensively elaborated. This study comprehensively addresses stability, electro-optic response, transport aspects, and mechanical features. The tolerance factor's calculated values and negative values predicted for formation energies have guaranteed the stability of the phase and thermodynamically, respectively. The electronic aspects have estimated the band gaps of K2CuAlCl6, K2CuAlBr6, and K2CuAlI6 that are 1.44 eV, 0.90 eV, and 0.41 eV, respectively. These band gaps are direct and reported materials are semiconductors demonstrating p-type characteristics. A detailed investigation of the light interaction with materials reveals that they exhibit significant absorbance (order of 105/cm) and conductivity in the visible spectrum. Based on this analysis of the optical response, it is evident that these compounds are valuable for utilization in photovoltaics. Thermoelectric performance analyzing parameters, including Seebeck coefficient, conductivity parameters, and figure of merit, have been described thoroughly. Born mechanical criteria fulfillment guarantees the stability of studied HDPs under stress. The elastic properties have yielded valuable information on anisotropy and elastic durability, and the ductile nature of a material is identified by Poisson's and Pugh's ratios. Hence, K2CuAl(Cl/Br/I)6 exhibit promising characteristics that make them viable competitors for harnessing energy objectives and sustainable technologies. © 2025 Elsevier Ltd