A First-principles Analysis of the Role of Biaxial Strains on Cubic FAPbCl₃ Perovskites

The remarkable structural, electrical, and optical properties of organic-inorganic perovskite materials have generated significant interest in their application in solar technologies. This study examined how bidirectional tensile and compressive strains together with the spin-orbit coupling (SOC) impact the structural, electronic, optical properties, and electronic properties of formamidinium lead chloride (FAPbCl₃) perovskites via a first-principles density-functional theory (DFT). The band structures of FAPbCl₃ without SOC showed that the perovskite structure has semiconductor properties with a direct bandgap. Application of compressive strains decreased the electronic bandgap. A 2% tensile strain resulted the bandgap to increase and for other tensile strains, the bandgaps decreased. The SOC's presence decreased the bandgap, causing the perovskite structure to transition from a direct bandgap to an indirect bandgap state. The dielectric constant indicated that the system maintains its semiconducting properties under compressive strains. It was also confirmed that the perovskite structure maintained it’s the semi-metallic behavior under tensile strains of +6% and +8%. The dielectric function, loss spectrum, and absorption coefficient peaks of FAPbCl₃ perovskites exhibited a shift towards longer energy region when subjected to compressive strains, and a shift towards shorter energy region when subjected to tensile strains. The FAPbCl₃ perovskites have favourable electronic and optical characteristics, making them appropriate for uses in optoelectronic devices.