Role of compressive and tensile strains and spin-orbit coupling on structure and behaviors of cubic FAPbI3 perovskites: A first-principles prediction

Organic-inorganic perovskite materials have attracted significant attention in solar technologies due to their extraordinary structural, electrical, and optical features. This study extensively examined the impacts of bidirectional tensile and compressive strains and spin-orbit coupling (SOC) on the structural, electronic and optical characteristics of formamidinium lead iodide perovskite (FAPbI3) structures. The investigation was performed using the first-principles density-functional theory (DFT). The electronic band structures of FAPbI3 without SOC revealed that the perovskite structure possesses the characteristics of a semiconductor, explicitly featuring a direct bandgap. The application of compressive strains resulted in dwindling the electronic bandgap while tensile strains upsurged the bandgaps, except at +6 % strains. The incorporation of the SOC subjugated a notable decrease in the bandgap, causing a transition of the perovskite structure from a direct bandgap to an indirect bandgap state. The real dielectric constant suggested that the system maintains its semiconducting character under the exposure of both compressive and tensile strains. The imaginary part of the dielectric function, loss spectrum, and absorption coefficient peaks of FAPbI3 perovskites exhibited a blueshift when subjected to compressive strains. However, the application of tensile strains eventuated in a redshift. The electronic and optical characteristics indicated that FAPbI3 perovskites have great potential for optoelectronic devices, including LEDs, LCD backlights, solar cells, lasers, and light detectors.