Elevating energy device potential: exploring optoelectronic and thermoelectric advantages in stable double perovskites K₂NaInX₆ (X = F, Cl, Br, I) via Ab initio analysis

By employing computational methods, this study contributes to a comprehensive understanding of the structural, optical and electron transport characteristics of K₂NaInX₆ (X = F, Cl, Br, I) double perovskite compounds, paving the way for potential applications in optoelectronic and thermoelectric devices. The physical properties of cubic K₂NaInX₆ (X = F, Cl, Br, I) double perovskite are investigated using density functional theory (DFT). The results of the formation energy (H) and tolerance factor (τ_G) tests demonstrate their cubic phase stability. The direct bandgap (E_g) values of K₂NaInF/Cl/Br/I₆ are 4.871, 2.454, 1.346 and 0.282 eV, respectively. The refractive index, absorption coefficient, reflectivity, and dielectric constants are also calculated. These calculations provide insights into the optical behavior and potential applications of the investigated double perovskite materials. In addition, the thermoelectric properties of K₂NaInF/Cl/Br/I₆ are evaluated using the BoltzTrap code. The calculated figure of merit (ZT) values for these compounds are found to be 0.8, signifying their suitability for thermoelectric applications. Moreover, the analysis of the structural and optoelectronic properties of K₂NaInX₆ (X = F, Cl, Br, I) compounds reveals their favorable photo-absorption characteristics, making them promising candidates for applications in solar cells and ultraviolet (UV) photodetectors.