For decades, solar power has been associated with rooftops, deserts, open fields and other places where sunlight is abundant. But researchers in China have now demonstrated something that once seemed almost impossible: a solar power system operating 33 feet (10 meters) below the sea surface.
A research team led by Zhang Wen-hua at Yunnan University developed an underwater photovoltaic system based on perovskite solar cells. The technology was tested in the South China Sea and successfully generated electricity from the weak blue-green light that survives at this depth.
The breakthrough could eventually provide a new way to power underwater sensors, cameras, communication equipment and other devices used for ocean exploration.
Why Put Solar Panels Underwater?
Modern ocean research increasingly depends on electrical equipment operating far below the surface. Sensors can monitor water conditions, cameras can observe marine life, and communication systems can help transmit information from underwater environments.
The biggest challenge is supplying these devices with reliable power.
Batteries can eventually run out and replacing them underwater can be difficult, expensive and sometimes dangerous. Connecting equipment to the surface with cables is another option, but cables can add complexity and restrict where instruments can be deployed.
Solar energy offers an attractive alternative because sunlight is available at the ocean surface. The challenge is that very little usable light remains as you go deeper underwater.
Previous research had already demonstrated underwater solar cells, but most systems had been tested only in relatively shallow water, generally around 6 feet (2 meters) or less.
The Yunnan University team wanted to push this much further.
Their target was 33 feet, or 10 meters, a depth that is more relevant to many underwater applications.
The Sunlight Problem Under the Sea
The deeper sunlight travels through seawater, the more it is absorbed.
Different wavelengths of light are absorbed at different rates. Red light disappears relatively quickly, while blue and green wavelengths penetrate much deeper.
This creates a major problem for conventional silicon solar cells because they are particularly effective across portions of the spectrum that become increasingly unavailable underwater.
At 10 meters, the researchers needed a solar material capable of making efficient use of the limited blue-green light.
Their solution was perovskite photovoltaics.
Perovskite solar cells are interesting because their optical and electronic properties can be tuned for different conditions. For this experiment, the researchers developed a perovskite material with a relatively wide 1.96-electron-volt band gap, designed to work better with the spectrum of light available in seawater.
In simple terms, instead of trying to make a conventional solar cell work with the sunlight that had already disappeared, the researchers designed the cell around the light that could actually reach it.
Making a Solar Cell Survive Seawater
Generating electricity underwater was only half the challenge.
The ocean is an extremely demanding environment for electronic equipment. Saltwater is corrosive, while increasing depth also brings higher pressure. Any tiny weakness in the protective structure could allow water to enter and damage the photovoltaic device.
The researchers therefore had to protect the solar cell without blocking the small amount of light reaching it.
They used several protective layers, including butyl rubber and cover glass, along with a transparent epoxy resin outer layer.
The resulting structure was designed to provide protection against water, pressure and corrosion while still allowing light to reach the solar cell.
The researchers also used polyhexamethylene guanidine hydrochloride (PHMG) as a crystallization additive to improve the stability of the perovskite material.
Surprisingly High Efficiency
The laboratory results were particularly interesting.
The researchers tested a tiny solar cell measuring only 0.014 square inches (0.0895 square centimeters) under simulated conditions corresponding to a depth of 33 feet.
It achieved a power-conversion efficiency of 34.71%.
A larger module measuring 4.46 square inches (28.79 square centimeters) achieved 29.4% efficiency.
These numbers are significant because the solar cells were operating under extremely weak underwater illumination rather than normal sunlight at the surface.
The results suggest that carefully engineered perovskite cells can still convert the limited blue-green light underwater into useful electrical power.
Can It Survive for Years?
Long-term durability is crucial if underwater solar power is ever going to become practical.
A solar cell that works brilliantly for a few hours but rapidly degrades in seawater would have little value for real-world ocean equipment.
The researchers therefore subjected their device to simulated seawater conditions.
After 1,000 hours of immersion, the device retained 99.58% of its initial power-conversion efficiency.
The researchers also reported a T80 lifetime of 48,904 hours at 25°C (77°F). T80 refers to the estimated time required for the device's performance to fall to 80% of its initial value.
If this lifetime estimate holds under practical operating conditions, it corresponds to more than five years.
That durability could be particularly important for underwater instruments that are difficult or expensive to retrieve for maintenance.
The Real-World South China Sea Test
The researchers didn't stop in the laboratory.
They took the technology into the South China Sea and tested it at three different depths: approximately 6 feet (2 meters), 18 feet (6 meters), and 33 feet (10 meters).
The underwater solar system was used to charge lithium-ion batteries.
After two hours of illumination, the batteries accumulated approximately:
1,416 mWh at 2 meters
752 mWh at 6 meters
324 mWh at 10 meters
As expected, the amount of energy collected decreased as the system moved deeper underwater.
But the important result was that the solar cell continued generating usable electricity even at 10 meters.
The stored energy was sufficient to power an LED panel, demonstrating that the system wasn't merely detecting tiny electrical signals—it could actually produce useful energy for a device.
What Could This Technology Be Used For?
The most realistic applications are likely to involve low-power underwater electronics rather than large-scale electricity generation.
For example, underwater solar systems could potentially help power:
Ocean-monitoring sensors
Underwater cameras
Environmental detectors
Communication equipment
Autonomous underwater instruments
Marine research equipment
Long-term monitoring stations
Instead of sending a maintenance team to replace batteries frequently, future underwater equipment could potentially recharge itself using sunlight.
This could be especially valuable for systems designed to remain underwater for long periods.
A New Direction for Solar Energy
Calling this a conventional "solar power plant" would be somewhat misleading—the demonstrated device is a small experimental photovoltaic system, not an underwater utility-scale power station.
But the experiment proves an important concept.
Solar energy doesn't necessarily have to stop at the ocean surface.
At 10 meters, sunlight is dramatically weaker and much of the red portion of the spectrum has already disappeared. Yet by using a wide-band-gap perovskite material and carefully engineered waterproof protection, the researchers were able to turn the remaining blue-green light into electricity.
The next challenge will be scaling up the technology while maintaining efficiency, durability and reliable operation in real ocean conditions.
If those challenges can be solved, underwater photovoltaics could become another tool for powering the growing network of sensors and machines exploring Earth's oceans.
Reference: Ma S, Cai B, Wang R et al., "Submerged solar harvesting with wide-band-gap perovskites for autonomous underwater energy systems" Joule, 2026. DOI: 10.1016/j.joule.2026.102672
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