A DFT study: Tailoring opto-electronic and thermoelectric performance of K2SeX6 (X = Cl, Br) double perovskites for solar cell advancements

Abstract

Density functional theory (DFT) has been used to examine the structure, optoelectronic, elastic, and thermoelectric characteristics of K2SeX6 (X= Br, Cl) utilizing the full potential linearized augmented plane wave (FP-LAPW). The examined double perovskites (DPs) appeared to feature indirect band gaps, according to the electronic band structure plots. K2SeX6 (X= Cl, Br) have computed shear anisotropy values of 0.55 and 0.54, respectively, indicating they are anisotropic materials. The materials' computed Poisson's ratios of 0.25 and 0.26 suggest that they are naturally ductile. According to the band structure plots, the examined DPs appear to feature indirect band gaps. The band gap values of two functional inorganic/organic perovskites, K2SeBr6 and K2SeCl6, are strikingly close to 2.0 eV and 1.689 eV. (Using modified Becke Johnson (mBJ) approximations). Because the maximum peaks occur in the visible and ultraviolet regions, they suggest potential solar cell applications for the materials. K2SeX6 (X=Br, Cl) has good values for electron production, great potential for applications in the optoelectronic sector. Additionally, it is a semiconductor by nature, according to the results of other optical characteristics such as absorption coefficients, electron energy loss, conductivity, and reflectivity. Because the maximum peaks occur in the visible and ultraviolet regions, they suggest potential solar cell applications for the solids. For K2SeX6 (X= Cl, Br), the computed Seebeck coefficient at 100 K, the S values attained 299.9 μV/K and 219 μV/K, respectively, are positive, demonstrating p-type conduction. Both K2SeBr6 and K2SeCl6 have a figure of merit values that are more than one (ZT > 1) 300K range which indicates that they are effective thermoelectric materials, but after these values of temperature, the zTe values vary. The computations' findings are the foundation for K2SeX6 (X= Cl, Br) and are practically applicable to solar cells.