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.
Two-dimensional (2D) lead halide perovskite with attractive properties is considered one of the most promising candidates for preparing blue-emitting materials and corresponding optoelectronic devices. For the formamidinium-based (FA) nanoplatelets (NPLs), despite exhibiting better optical performance compared to their counterparts, it is still challenging to precisely control their emission in the blue region during synthesis and the influence of chloroform on the components of FAPbBr 3 have not been investigated thoroughly. Herein, it is revealed that the decomposition of chloroform during the synthesis will introduce Cl into the crystal with the assistance of surface ligands, leading to the mixed-halide perovskite. Further, an A-site cation strategy was introduced for tuning the spectra of FAPbBr 3 NPLs. The addition of Cs with a small ionic radius can shrink the arrangement of octahedrons and enhance their interactions, which will promote the seeding growth of perovskite and form uniform crystals. With help of surface ligands, these uniform crystals will further grow to form homogeneous perovskite NPLs. The obtained NPLs show the pure emission from sky-blue to deep-blue. To the best of our knowledge, it is the first report about finely tuning the emission of FAPbBr 3 in the blue region. This crystallization control strategy by introducing Cs is beneficial for their further applications in the field of photoelectric devices.
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