Exploring the Optoelectronic Potential of Cubic Halide-Perovskite KFeX3 (X = Cl, Br): A DFT Perspective

The present work deals with exploring the electronic, optical, and structural properties of cubic halide-perovskites KFeX3 (X= Cl, Br) through first-principles calculations. The study used the CASTEP code with the PBE exchange-correlation functional in the GGA framework. Ultra-soft pseudo-potential (USP) plane-wave. DFT calculations were carried out for this study. The calculated elastic constants of KFeCl3 and KFeBr3 in their cubic phases supported their mechanical stability. Applying Pugh´s criteria, it is clear that neither of the materials is classified as a brittle material. Electronic band structure analysis indicates that KFeCl3 has an indirect band gap and KFeBr3 possesses a direct band gap, which is consistent with previous reports. Moreover, partial density of states (PDOS) and total density of states (TDOS) were also employed to analyze the electron localization of various bands. Peaks were fitted to the dispersion relation of a hypothetical dielectric function to determine the optical transitions within these compounds. These materials are insulating at 0 K and semiconductors above 0 K rather like the normal BCS metals. The real part of the dielectric function is rather flat with the energy, while the imaginary part of the dielectric function displays a broad spectral width with the energy, which achieves the overall transparency of the inevitable UV-active optoelectronic devices.