New Type of Solar Cell has More than Double Efficiency

Scientists have developed new heat-resistant materials that could be used to make more efficient solar energy devices that do not waste as much heat as traditional components. 

Converting heat into infrared light allows solar cells to absorb it and make electricity, a process known as thermophotovoltaics. Previous attempts to design an efficient thermophotovoltaic system have fizzled, with experiments in the past falling apart under the heat.

This new material, a compound of tungston and ceramic, can be used to make a heat-resistant thermal emitter, which can remain stable at temperatures up to 2,500 degrees Fahrenheit.

"This is a record performance in terms of thermal stability and a major advance for the field of thermophotovoltaics," said Shanhui Fan, a professor of electrical engineering at Stanford University, who published a paper with his colleagues in the journal Nature Communications.

A typical solar cell has a silicon semiconductor that absorbs sunlight and converts it directly into electrical energy, but they are not very efficient and only respond to infrared light. Higher-energy light waves, including most of the visible light spectrum, are wasted as heat, while lower-energy waves simply pass through the solar panel, the researchers wrote in a statement.

"In theory, conventional single-junction solar cells can only achieve an efficiency level of about 34 percent, but in practice they don't achieve that," said study co-author Paul Braun, a professor of materials science at Illinois. "That's because they throw away the majority of the sun's energy."

The team attempted to overcome that limitation with thermophotovoltaics and a specialized, heat resistant thermal emitter.

"Essentially, we tailor the light to shorter wavelengths that are ideal for driving a solar cell," Fan said. "That raises the theoretical efficiency of the cell to 80 percent, which is quite remarkable."