Researchers led by Simin Ma at Yunnan University have developed a perovskite solar cell designed to generate electricity underwater, potentially powering devices such as uncrewed underwater vehicles and submerged sensors. Perovskite cells are cheaper and more efficient than traditional silicon panels but usually degrade quickly, especially when exposed to moisture, making underwater use seem counterintuitive. However, because perovskites can be tuned to absorb the specific wavelengths of light that penetrate water, and because cooler, dimmer underwater conditions actually reduce degradation, the team saw an opportunity to overcome this weakness.

The breakthrough came from an additive, polyhexamethylene guanidine hydrochloride, which forms a water-repelling layer and strengthens the perovskite's crystal structure, significantly improving durability. Under simulated light matching a depth of around 10 metres, the cells converted about 35 percent of light energy into electricity, compared with roughly 20 percent for silicon panels. After 40 days submerged in seawater, the cells retained 99.6 percent efficiency, leading researchers to estimate a working lifespan of about 5.5 years before dropping to 80 percent efficiency. Real-world tests in the South China Sea, charging coin-cell batteries at depths of 2, 6 and 10 metres, confirmed reliable performance, though output fell to roughly a quarter of surface levels at 10 metres.