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 <i>Pn</i> 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 <i>V</i>_oc ∼ 0.52 V and <i>J</i>_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.