Solar cell prototype breaks efficiency record

A team of Midwestern researchers had a solar technology breakthrough that could result in more energy-efficient, higher-voltage solar cells. 

Engineers from Northwestern University, the University of Toledo, and the University of Toronto created a new type of solar cell that doesn’t contain silicon, a material that is energy-intensive to produce and purify. Instead, they used two layers of perovskites, crystalline nanomaterials. 

“While silicon solar cells have undergone impressive advances in recent years, there are inherent limitations to their efficiency and cost, arising from material properties,” said Ted Sargent, Northwestern professor, in a statement. “Perovskite technology can overcome these limitations, but, until now, it had performed below its full potential.” 

The solar cell prototype is small: just one square centimeter that produces 2.19 electron volts. But that’s a record for perovskite solar cells. It achieved 27.4% power-conversion efficiency, which is a record that beats even silicon solar cells.

Developers can fine-tune which wavelengths of light are absorbed and converted to electricity by adjusting the perovskites’ thickness and chemical composition. For example, one layer could absorb the ultraviolet part of the light spectrum and another could absorb the infrared part. By contrast, silicon always absorbs the same, limited parts of the spectrum.

The team’s big finding occurred when analyzing the touchpoints between the perovskite layers. They discovered that the electrons didn’t all move uniformly between the two, so they coated it with a substance called PDA. The coating improved the layers’ alignment and increased efficiency. 

The researchers hope to further improve the solar cell efficiency and stability in addition to scaling production for commercial use.
“In the last 10 years, perovskite technology has come almost as far as silicon has in the last 40,” said Ph.D. student Aidan Maxwell. “Just imagine what it will be able to do in another 10 years.”

Photo by Aaron Demeter / University of Toronto