Polarization Effects on Electronic and Optical Properties in FAPbX3 (X = I, Br, Cl) Perovskites

Here we show that in FAPbX3 (X = I, Br, Cl) the polarization enhances visible-light absorption, reduces carrier effective mass anisotropy, and significantly lowers exciton binding energy in FAPbI3 compared to FAPbBr3 and FAPbCl3, attributed to its higher dielectric constant and enlarged exciton Bohr radius. Notably, polarization-induced dielectric screening and lattice distortion synergistically weaken electron–hole Coulomb interactions, facilitating efficient charge separation. These findings underscore polarization engineering as a critical strategy for optimizing charge transport and light harvesting in perovskite-based optoelectronics. Notably, the spectroscopic limited maximum efficiency (SLME) of polar phases FAPbX3 shows up to 36% improvement compared to nonpolar phases, attributed to polarization-mediated enhancement of carrier transport. Our findings demonstrate that the polarization-structural distortion synergy serves as a key mechanism driving efficiency enhancement in FAPbX3 perovskite photovoltaics.