Hot-cold design supercharges solar thermoelectric efficiency by 15x

University of Rochester researchers have developed a way to make solar thermoelectric generators (STEGs) 15 times more powerful, potentially closing the efficiency gap with conventional solar panels and opening new possibilities for renewable energy.

Unlike the photovoltaic cells used in most solar panels, STEGs can tap into various heat sources in addition to sunlight.

The devices operate by exploiting the temperature difference between a hot side and a cold side, with semiconductor materials in between, generating electricity through the Seebeck effect.

However, STEGs have faced a significant limitation: most convert less than 1% of sunlight into electricity, far below the roughly 20% efficiency achieved by residential photovoltaic systems.

That may change thanks to new spectral engineering and thermal management methods from the University of Rochester’s Institute of Optics.

In a study, researchers described a system that dramatically improved output without altering the semiconductor materials themselves.

“For decades, the research community has been focusing on improving the semiconductor materials used in STEGs and has made modest gains in overall efficiency,” said Chunlei Guo, a professor of optics and of physics and a senior scientist at Rochester’s Laboratory for Laser Energetics.

“In this study, we don’t even touch the semiconductor materials—instead, we focused on the hot and the cold sides of the device.

By combining better solar energy absorption and heat trapping at the hot side with better heat dissipation at the cold side, we made an astonishing improvement in efficiency.”

Supercharging the hot ride

The team’s approach relied on three main innovations. First, on the hot side of the STEG, they applied a “black metal” technique developed in Guo’s lab.

Using femtosecond laser pulses, they etched nanoscale structures into tungsten, enabling it to selectively absorb light at solar wavelengths while reducing heat loss at other wavelengths.

Second, they created a miniature greenhouse effect by covering the black metal with a piece of plastic. This layer limited convection and conduction, allowing more heat to be trapped and raising the temperature on the hot side.

“You can minimize the convection and conduction to trap more heat, increasing the temperature on the hot side,” Guo said.

Maximizing the cold side

On the cold side, the team again used femtosecond laser pulses—this time on aluminum—to produce a highly effective heat sink.

The process created tiny structures that boosted heat dissipation through both radiation and convection, doubling the cooling performance of a standard aluminum dissipator.

The new design demonstrated significant real-world potential. In tests, the upgraded STEGs powered LEDs much more effectively than earlier devices.

According to Guo, the technology could be adapted to power wireless sensors for the Internet of Things, wearable devices, or off-grid renewable systems in rural areas.

The work was supported by the National Science Foundation, FuzeHub, and the Goergen Institute for Data Science and Artificial Intelligence.

The findings were published in Light: Science and Applications.