Visible‐Photoactive Ferroelectric Semiconductor Incorporating Aromatic Dynamic Spacer Enables Optoelectronic Synaptic Plasticity

Abstract Photoferroelectrics are capturing the growing interest for their unique light‐polarization coupling and optoelectronic applicability. However, the formidable challenge persists in coupling electric order and strong photoactivity through precise molecular design, hindering their further application in the field of optoelectronic memory. Herein, the molecular dynamics of aromatic cations in the 2D constrained environments are customized to construct perovskite photoferroelectrics, (4‐ tert ‐butylbenzylammonium) 2 (ethylammonium) 2 Pb 3 I 10 , showing a narrow bandgap (≈1.96 eV) and strong visible‐photosensitivity. Notably, multi‐level dynamic states of aromatic cations provide the impetus for inducing ferroelectric order and photo‐ferroelectric effects. Such captivating characteristics can achieve light‐induced multiple polarization, dielectric, and conductivity states. Accordingly, photoferroelectrics are integrated into heterojunction phototransistors that display robust electrical and optical modulation, including diversified synaptic plasticity with low optical program power (≈20 pJ) for each training process. As a noteworthy advancement in the photoferroelectric field, this work will enrich the understanding of the structure‐property relationship and shed light on further exploration toward neuromorphic computing.