研究人员揭开能级排列之谜

Solar power may be on the rise, but solar cells are only as efficient as the amount of sunlight they collect. Under the direction of a new McCormick professor, researchers have developed a new material that absorbs a wide range of wavelengths¹ and could lead to more efficient and less expensive solar technology. A paper describing the findings, "Broadband polarization-independent resonant² light absorption using ultrathin plasmonic super absorbers," was published November 1 in the journal Nature Communications.

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"The solar spectrum³ is not like a laser -- it's very broadband, starting with UV and going up to near-infrared," said Koray Aydin, assistant professor of electrical engineering and computer science and the paper's lead author. "To capture this light most efficiently⁴, a solar cell needs to have a broadband response. This design allows us to achieve that." #

The researchers used two unconventional materials -- metal and silicon⁵ oxide⁶ -- to create thin but complex, trapezoid（梯形的） -shaped metal gratings on the nanoscale that can trap a wider range of visible light. The use of these materials is unusual because on their own, they do not absorb light; however, they worked together on the nanoscale to achieve very high absorption rates, Aydin said. #

The uniquely shaped grating（光栅） captured a wide range of wavelengths due to the local optical resonances⁷, causing light to spend more time inside the material until it gets absorbed. This composite metamaterial（特异材料） was also able to collect light from many different angles -- a useful quality when dealing⁸ with sunlight, which hits solar cells at different angles as sun moves from east to west throughout the day. #

This research is not directly applicable to solar cell technology because metal and silicon oxide cannot convert light to electricity; in fact, the photons are converted to heat and might allow novel ways to control the heat flow at the nanoscale. However, the innovative⁹ trapezoid shape could be replicated¹⁰ in semiconducting materials that could be used in solar cells, Aydin said.

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If applied¹¹ to semiconducting materials, the technology could lead to thinner, lower-cost, and more efficient solar cells, he said. #