Enhancing the optoelectronic performance of ABX ₃ perovskites (A=MA+/FA+, B=Pb2+, X=I ⁻ /Br ⁻ ): A comprehensive first-principles investigation for next generation solar cell technology

In this study, Hybrid halide perovskites, specifically MAPbI 3 and FAPbBr 3 , are examined using Density Functional Theory to investigate their structural, electronic, and optical properties. The optimization of structures reveals a typical ABX 3 structure, with methylammonium (MA[Formula: see text]) and formamidinium (FA[Formula: see text]) acting as A-site cations, each fulfilling its distinct role. Analyzing the band structure reveals that spin-orbit coupling has a significant impact, altering band edges and narrowing the bandgap. Density of states and projected density of states analyses reveal the influence of spin-orbit coupling on orbital contributions, primarily from FA[Formula: see text] and Br − , which increases the valence band density. Optical properties, measured using the dielectric function, absorption spectra, and Tauc plots, show that MAPbI 3 absorbs visible light better, while FAPbBr 3 responds more broadly at higher energies. Both strain engineering and chemical substitution offer practical ways to tune the bandgap, which is essential for integrating devices. Electron localization function (ELF) maps reveal strong electron localization, particularly around Pb due to lone-pair electrons, and halide ions contribute to ionic bonding. Analysis of charge density difference (CDD) indicates FA[Formula: see text] causes a more thorough electron redistribution than MA[Formula: see text], which might suggest better structural stability and increased electronic coupling in FAPbBr 3 . In most cases, this study provides a detailed examination of the relationship between structure and properties in hybrid perovskites for optoelectronic applications.