New depths for subsea solar

Researchers have developed solar cells that can function 10 metres underwater, potentially powering submerged sensors, cameras and communications systems far from land.

The Chinese and Swiss scientists tested out the cells at a depth of 10 metres below the surface of the South China Sea, where they found that they could generate 324 megawatt-hours of energy — enough to charge lithium-ion batteries — when submerged for two hours. They also found the cells could operate continuously at the 10-metre depth for about 5.5 years.

Their study has been published in the Cell Press journal Joule.*

“Very few studies have been reported on underwater solar cells, and all of them are focused on very shallow water depths of only two metres or less, a scenario far from catering for requirements of practical application,” said 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 metres, greatly broadening their application scope.”

While photovoltaics have long been successful on land, researchers have struggled to harvest solar energy beneath the sea for monitoring aquaculture and other uses, as sunlight quickly drops in intensity over short distances underwater. To overcome this hurdle, Zhang’s team first developed a customised 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 most efficient with wide bandgaps: a feature that allows them to absorb blue to orange light. After being stored in a glovebox filled with nitrogen gas for 300 days, the solar cells were found to have retained about 96% of their initial efficiency. They also showed almost no degradation after 1160 hours under simulated conditions at a depth of 10 m, suggesting high durability underwater.

The next step was to integrate perovskite solar cells with underwater robots, deploying them at a depth of 10 m off the Weizhou Islands in the South China Sea to test their real-world applications.

According to Zhang, the cells exhibited “exceptional” long-term operational stability.

“What surprised us most was [how] much electrical energy our large-area modules generated under real-world conditions at 10-metre water depth for only two hours,” he said.

“Moreover, we have achieved scaling from small‑area laboratory cells to large‑size modules.

“The combination of the laboratory investigations and the in-field experiments provides strong evidence for the operation of underwater photovoltaics.”

Next, 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 standardised testing protocols for underwater photovoltaics.

_{*‘Submerged solar harvesting with wide-band-gap perovskites for autonomous underwater energy systems’, DOI: 10.1016/j.joule.2026.102672.}

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