Giant Bulk Photovoltaic Power Generation in 2D AgBiP2Se6 Crystals

With the theoretical high power conversion efficiency (PCE) exceeding the thermodynamic Schockley–Queisser (S–Q) limit, the bulk photovoltaic (BPV) effect, which is manifested in acentric crystals across the entire visual spectrum, holds great potential for next‐generation light‐harvesting devices. Here the abnormally giant second harmonic generation (SHG) activity and BPV response in 2D AgBiP2Se6 crystals with broken inversion symmetry is demonstrated, which can be remarkably enhanced with the thickness downscaling. Based on the vertical device sandwiched with graphene electrodes, the wideband light absorption of 2D AgBiP2Se6 crystals with Eg of 1.49 eV enables giant BPV response in the entire visible spectrum, and efficient utilization of solar energy contributes to large short‐current (≈330 mA cm−2), high PCE (≈0.13%) and EQE (≈12.5%) under 532 nm light illumination. Furthermore, benefitting from the local ion redistribution driven by an in‐plane electric field, the BPV photocurrent generation is effectively enhanced 3 times, yielding an extremely high PCE of 0.18%, according high among the reported 2D acentric crystals. The study reintroduces AgBiP2Se6 to the 2D acentric crystal family and lays the groundwork to develop BPV devices for light‐harvesting applications.