Solar panels have become a familiar sight on rooftops and in fields, but they aren’t the only way to turn sunlight into electricity.
Another type of technology, called solar thermoelectric generators (STEGs), has the potential to tap not just sunlight, but almost any kind of heat source—turning temperature differences directly into power.
STEGs are simple devices. They have a hot side and a cold side, with semiconductor materials sandwiched in between.
When there’s a difference in temperature between the two sides, electricity is generated through something called the Seebeck effect—a well-known physical phenomenon.
But while the concept sounds promising, there’s been one big problem: efficiency.
Most current STEGs convert less than 1% of sunlight into electricity, while the solar panels on homes typically reach around 20%.
This huge gap has held back STEGs from becoming a practical energy source.
But researchers at the University of Rochester’s Institute of Optics believe they’ve found a way to bridge that gap—and the results are dramatic.
In a study published in Light: Science and Applications, the team reports that their new design generates 15 times more power than previous STEGs. The key?
Instead of trying to improve the semiconductor materials, which is where most researchers have focused for decades, they looked at the hot and cold surfaces of the device and re-engineered them for maximum performance.
Chunlei Guo, a professor of optics and physics at Rochester and a senior scientist at the university’s Laboratory for Laser Energetics, led the work. “We didn’t touch the semiconductors at all,” Guo explained. “Instead, we worked on getting more heat to the hot side and better cooling on the cold side—and the efficiency improvement was astonishing.”
The hot side of the STEG got a complete makeover thanks to Guo’s “black metal” technology. Using incredibly short bursts of laser light—called femtosecond pulses—the researchers etched nanoscale patterns onto regular tungsten metal. These patterns transformed it into a highly efficient light absorber, selectively capturing solar wavelengths while minimizing heat loss at other wavelengths.
To boost the effect even more, they covered the black metal with a piece of plastic, creating a tiny greenhouse. Just like the glass on a greenhouse traps warmth for plants, this plastic covering reduced heat loss through convection and conduction, making the hot side even hotter.
On the cold side, the team turned their laser onto regular aluminum, carving out microscopic structures that dramatically improved its cooling abilities. This specially engineered heat sink released heat through both radiation and convection, doubling the cooling performance compared to ordinary aluminum.
The result of combining these three strategies—a black metal hot side, a mini greenhouse layer, and a super-cooled aluminum cold side—was a STEG that could power LEDs far more effectively than previous versions.
Guo says the potential uses for the technology go beyond lighting. These improved STEGs could provide power for wireless sensors in the Internet of Things, wearable electronics, or off-grid renewable energy systems in rural areas.
By making STEGs more efficient, the breakthrough could open the door to new ways of harnessing solar energy, helping to bring the world closer to true energy independence.
Source: University of Rochester.
