A review on theoretical studies of structural and optoelectronic properties of FA-based perovskite materials with a focus on FAPbI3

Organic-inorganic hybrid perovskite materials have captured many researchers' interest in solar cell application during the last decade. Due to their astonishing photoelectric properties and rapid increase in efficiency, these materials are promising candidates for affordable solar cell technologies and optoelectronic devices. Also, with respect to their high-power conversion efficiency (PCE), cost-effectiveness, gap tunability, longer charge diffusion length, much improved photochemical and thermal stability, formamidinium (FA)-based perovskites are one of the most promising materials as well. However, the easy formation of non-perovskite delta-phase formamidinium at low temperatures and toxic Pb is disadvantageous. It is worth mentioning that various strategies have been developed to stabilize alpha-phase FAPbI(3) at room temperature and decrease the toxicity of lead element while retaining their good performances. The current review highlights the recent theoretical progress in stabilization, bandgap engineering, and optical performance of these promising materials.