Superabsorbing Method Improves Solar Cell Efficiency

A newly designed superabsorbing solar cell has the potential to significantly improve the light absorption efficiency of thin-film solar cells without compromising solar light absorption capabilities.

Developed by a team at North Carolina State University, the design could reduce the thickness of the semiconductor materials used in thin-film solar cells by an order of magnitude or more.

“A decrease in the thickness of semiconductor materials by one order of magnitude would mean a substantial improvement in manufacturing productivity and reduction in cost,” said researcher Dr. Linyou Cao, an assistant professor of materials science and engineering at NCSU.

The new superabsorbing design could make light absorption in thin-film solar cells more efficient. Courtesy of NCSU.

The deposition of semiconductor materials is a major hindrance to improvement in manufacturing productivity and to lowering the cost of thin-film solar cells, he said. These cells have been shown to use less material, allowing the thin films to be deposited more quickly.

In their study, the researchers used light-trapping techniques to examine the maximum absorption efficiency of semiconductor materials. To maximize solar absorption, they found that the amount of solar light trapped inside the structure must match the amount of solar light that can be absorbed.

The new design looks like a rectangular onion and matches light-trapping efficiency with the semiconductor’s light-absorbing efficiency in thin-film solar cells. The core is coated with a light-absorbing semiconductor material, then topped with three layers of nonabsorbing, antireflection coating.

“State-of-the-art thin-film solar cells require an amorphous silicon layer that is about 100 nm thick to capture the majority of the available solar energy,” Cao said. “The structure we’re proposing can absorb 90 percent of available solar energy using only a 10-nm-thick layer of amorphous silicon.”

Existing models of such solar cells have been unable to determine the upper limit of absorption of real semiconductor materials. The researchers expect their design will fundamentally solve the light-absorption efficiency problems.

The research was published in Scientific Reports (doi: 10.1038/srep04107).

For more information, visit: www.ncsu.edu