High-Temperature Molecular Ferroelectric [C4N2H14]2[Sb2I10] with Narrow Bandgap and Switchable Photoelectric Response

Organic–inorganic hybrid ferroelectrics have attracted considerable attention due to their outstanding piezoelectricity, mechanical flexibility, and robust nonlinear optical properties. But the species with above room-temperature (RT) ferroelectricity, visible-light bandgap, and high photoelectric performance are still scarce. Herein, a novel organic–inorganic hybrid ferroelectric [C₄N₂H₁₄]₂[Sb₂I₁₀] has been synthesized hydrothermally and employed as a light-absorbing layer in organic–inorganic hybrid solar cells. A polar monoclinic structure with a space group of Pn was resolved by single-crystal XRD. A direct band gap of 1.89 eV was revealed in [C₄N₂H₁₄]₂[Sb₂I₁₀] by UV–vis spectroscopy and density functional theory (DFT) studies. A dramatic enhancement in photoelectric performance has been achieved by turning the ferroelectric polarization, leading to a maximum V_oc ∼ 0.52 V and J_sc ∼ 15.52 μA/cm², which are 15-fold and 29-fold higher than those of the unpoled sample, respectively. This work may open new avenues for the application of molecular ferroelectrics in optoelectronic devices.