Electronic Structural, Optical and Elastic Properties of K-Based Lead-Free Perovskites KXF3 (X = Nb, Ti, Zr) via DFT Computational Approach

Perovskites are considered emerging materials for use in solar cells and thermoelectric generators and renewable energy due to their high stability, lack of lead content, environmentally friendly nature, and exceptional performance. Hence, a comprehensive study of the structural, optical, electronic and elastic properties of KXF 3 (X = Nb, Ti, Zr) was conducted using a first-principles approach. The structural stability of the material was confirmed by examining its formation energy, Gold-Schmidt tolerance and Birch-Murnaghan equation of state (EOS) curve. The negative formation energy for these compounds represents the structural stability.The electronic study reveals that in spin down configuration there is band gap between valence and conduction bands while in spin up configuration the valence and conduction bands are overlapped at fermi level indicating that understudy compounds are half metallic. The elastic constants relationship, namely C 11 – C 12 > 0, C 11 > 0, C 11 + 2C 12 > 0, and B > 0, establishes the mechanical stability of compounds. However, these materials are also identified as being mechanically brittle, anisotropic, and ductile. For checking the suitability of the studied compounds in the optical applications, we determined the real and imaginary parts of their respective dielectric functions, absorption coefficients, optical conductivities, refractive index and lastly reflectivity as a function of wide range of incident photon energies upto 40 eV. The study of these compounds reveals that they can be potential candidates for optoelectronic devices.