Scientists have taken solar cells to new depths, demonstrating that they can function 10 meters below the surface of the South China Sea. The study, publishing September 11 in the Cell Press journal Joule, found that solar cells could generate 324 mWh of energy—enough to charge lithium-ion batteries—when submerged for two hours and could operate continuously at the 10-meter depth for about 5.5 years. The findings suggest that underwater solar cells may be able to power submerged sensors, cameras, and communication systems far from land.
"Very few studies have been reported on underwater solar cells, and all of them are focused on very shallow water depths of only two meters or less, a scenario far from catering for requirements of practical application," says author Wen-Hua Zhang of Yunnan University and Southwest United Graduate School in Kunming, China.
"This work presents the first functional validation of submerged solar cells practically operating at a water depth of up to about 10 meters, greatly broadening their application scope."
While solar cells have long provided green energy to power technologies on land, researchers have struggled to harvest solar energy beneath the sea for monitoring aquaculture and other uses since sunlight quickly drops in intensity over short distances underwater. To overcome this hurdle, Zhang's team first developed a customized laboratory system with tailored optical filters to simulate underwater illumination at various depths.
During the lab experiments, the researchers determined that the submerged solar cells they developed were among the most efficient with wide bandgaps, a feature that allows them to absorb blue to orange light. After storing the cells in a glovebox filled with nitrogen gas for 300 days, the solar cells retained about 96% of their initial efficiency. They also showed almost no degradation after 1,160 hours under simulated conditions at a depth of 10 meters, suggesting exceptional durability underwater.
Next, the team integrated perovskite solar cells with underwater robots, deploying them at a depth of 10 meters off the Weizhou Islands in the South China Sea to test their real-world applications. The cells exhibited "exceptional" long-term operational stability, says Zhang.
"What surprised us most was so much electrical energy our large-area modules generated under real-world conditions at 10-meter water depth for only two hours," says Zhang.
"Moreover, we have achieved scaling from small‑area laboratory cells to large‑size modules," says Zhang. "The combination of the laboratory investigations and the in-field experiments provides strong evidence for the operation of underwater photovoltaics."
In future research, Zhang's team plans to test perovskite solar cells at deeper water depths, investigating the limit at which underwater solar cells can operate, and to establish standardized testing protocols for underwater photovoltaics.
