Bulk Photovoltaic Effect in High-Temperature Lead-Halide Molecular Ferroelectric [C₄N₂H₁₄][PbI₄]

Hybrid organic-inorganic molecular ferroelectrics (HOIMFs) have garnered significant attention owing to their potential applications in optoelectronic and spintronic devices. However, HOIMFs with high Curie temperature (T_c), narrow bandgap (E_g), excellent stability, and high breakdown voltage are still very rare. Herein, we present a novel lead-halide molecular ferroelectric, (1,4-butanediammonium)PbI₄ (1), synthesized hydrothermally. 1 exhibits a ferroelectric-to-paraelectric phase transition with a high Curie temperature of 485 K, a room temperature ferroelectric hysteresis loop with a robust saturation polarization of 3.9 μC/cm² and strong coercivity of 33 kV/cm, and a typical semiconductor behavior with a direct bandgap of 2.28 eV. Switchable photovoltaic effect was observed in 1-based device with a fast response time of ∼2 ms and high breakdown electric field of 80 kV/cm. Dramatically enhanced photovoltaic performance has been achieved by manipulating the ferroelectric polarization, resulting in a maximum photovoltage of V_oc ∼ 0.84 V and a photocurrent of J_sc ∼ 33.31 nA/cm² under standard AM 1.5 G illumination. This study offers a bright avenue for advancing high-T_c lead-halide molecular ferroelectrics with promising potentials in photodetectors, data storage, and logical switching devices.