Photoelectric-Coupled Ferroelectric Heterojunctions for Ultrahigh NO₂ Sensing With Polarization-Memory-Assisted...

Ferroelectric oxide heterostructures coupling optical, electrical, and chemical stimuli offer a compelling pathway toward multimodal artificial sensory systems mimicking biological perception. We report all-Aurivillius-phase Bi₂WO₆/SrBi₂Ta₂O₉ (BWO/SBT) heterojunction that integrates light-driven ferroelectric polarization switching, photoelectric memory, and gas sensing within a single architecture. Epitaxial BWO (∼65 nm) and ultrathin SBT (∼5 nm) films were grown in situ by laser molecular beam epitaxy, forming a coherent interface that enables visible-light-induced polarization reversal and persistent photoconductivity (PPC). The interfacial band bending, photoinduced charge screening, and polarization realignment dramatically enhance gas-sensing performance, achieving 530% (301%) NO₂-response at 10 ppm (0.3 ppm) -approximately 300-fold higher than the electrically pre-polarized counterpart. The PPC-enhanced sensor delivers a 0.46 ppb detection limit and 129.7% ppm^-1 sensitivity, representing one- and two-order-of-magnitude enhancements over electrically polarized (5.2 ppb, 11.5% ppm^-1) and unpoled (17.5 ppb, 3.42% ppm^-1) devices, respectively. It also exhibits exceptional stability, maintaining strong responses at 10°C-100°C and robust humidity tolerance (coefficient of variation < 4% from 5%-86% RH). This work provides experimental evidence supporting a non-linear interaction consistent with optoelectronic memory-mediated ferroelectric coupling, as a powerful strategy to modulate charge-transfer kinetics, offering a universal framework for self-adaptive gas sensors and multimodal bioinspired devices.