Interface Engineering Enhances the Photovoltaic Performance of Wide Bandgap FAPbBr3 Perovskite for Application in Low‐Light Environments

Abstract Underwater solar cells (UWSCs) provide an ideal alternative to the energy supply for long‐endurance autonomous underwater vehicles. However, different from conventional solar cells situated on land or above water, UWSCs give preference to use wide bandgap semiconductors (≥1.8 eV) as light absorber to match underwater solar spectra. Among wide bandgap semiconductors, FAPbBr 3 perovskite is under prime consideration owing to its matching optical bandgap (≈2.3 eV), outstanding photoelectric properties, easier processability, etc. Unfortunately, for FAPbBr 3 solar cells, substantial interface defects greatly limit the charge carrier extraction efficiency, thus limiting the device performance, especially in underwater low‐light environments. This study employs a molecular self‐assembly strategy to effectively eliminate the interfacial defects. As a result, a great improvement in power conversion efficiency (PCE) from 6.44% to 7.49% is obtained, which is among the best efficiency reported for inverted FAPbBr 3 solar cells up to date. Besides, a champion PCE of 30% is obtained under 520 nm monochromatic light irradiation (4.8 mW cm −2 ). These results demonstrate that FAPbBr 3 solar cells present a tremendously promising application in UWSCs.