Broad Power-Range Operable FAPbBr3:FABr Underwater Photovoltaics

Abstract

Lead bromide perovskites are highly promising for underwater photovoltaics (UPVs) due to their optimal bandgap alignment with the blue-green optical transmission window of water. However, underwater light environments─spanning from feeble deep-sea sunlight to intense artificial lasers─present an exceptionally wide dynamic range of light intensity. Designing high-efficiency UPVs requires precise control of carrier dynamics to maintain stable conversion efficiency across this wide range. In this work, we demonstrate that suppressing nonradiative recombination and minimizing series resistance are essential prerequisites for mitigating losses in the low- and high-power regimes, respectively. Furthermore, the introduction of excess FABr to form FAPbBr3:FABr augments short-circuit current density by promoting exciton dissociation and charge transfer across the entire range. Consequently, the optimized UPVs exhibit high power conversion efficiency (PCE) from weak simulated sunlight to intense 520 nm laser irradiation. Notably, the device achieved a stabilized efficiency of 43.4% under the most intense laser (535 mW/cm2) and maintained 84% of its initial performance after 50 h of continuous operation immersed in water.