Plasmonic near-field enhances photoelectrics in a Fabry–Pérot cavity heterostructure

Fabry–Pérot (F–P) cavities integrated with plasmonic nanostructures offer an effective platform for enhancing light–matter interactions, yet simultaneously achieving >90% broadband absorption across visible-NIR range and strong near-field enhancement remains challenging due to intrinsic spectral limitations of plasmonic resonators and complex cavity design. Herein, a hierarchical wheat spike-shaped plasmonic F–P–like cavity photoelectrode (Au-NP@TNW/Au-PL) is synthesized through the alkaline thermal treatment and visible-light-driven photoreduction process. This hybrid architecture exhibits an average absorption of 92% across 400-1080 nm and strong broadband near-field electromagnetic enhancement, as revealed by two-photon-induced photoluminescence measurements. This response arises from cooperative coupling between F–P cavity modes and nanoparticle plasmons, enabling broadband excitation and effective energy concentration near the plasmonic nanostructures. This coupling also shortens the plasmon dephasing time, indicating increased damping through interfacial charge transfer that converts plasmon energy into hot carriers. Consequently, Au-NP@TNW/Au-PL exhibits a photocurrent density nine times higher than TNW/Au-PL under solar irradiation, demonstrating strong potential for solar-driven hydrogen production. Plasmonic Fabry–Pérot cavities enhance light–matter interactions, but broadband absorption and near-field enhancement remain challenging. Here, the authors synthesized a plasmonic Fabry–Pérot–like photoelectrode with broadband absorption and strong field enhancement, resulting in a ninefold increase in photocurrent density.