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Nanostructures Catch the Light

Razor-thin solar cells could be cheap but need a little help holding light in

2 min read

Efficiency may be the first parameter you think of when you hear the word photovoltaics. However, a less-talked-about factor can have a big impact, too—how thin a solar cell is. Researchers have recently come up with new ways of slimming down cells using structures smaller than the wavelengths of visible light.

"The main aim is to use as little material as possible to absorb sunlight," says Shanhui Fan, associate professor of electrical engineering at Stanford. High-efficiency materials, such as III-V semiconductors and crystalline silicon, are expensive. With other materials such as amorphous silicon, cost is less of an issue, but the electrons and holes that carry charge travel only short distances before being lost as heat. "The thinner the cell gets, the easier it is to get the carrier out," Fan explains. However, the thinner a solar cell is, the more likely that photons will pass right through it before they can be absorbed.

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Greg Mably


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