Ultrathin Solar Material Traps Light, Hall-Of-Mirrors Style

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Solar cells have become so thin they almost look like silver leaf sheets, but the trick is making them as efficient as their thicker predecessors. Stanford University engineers think they’ve figured out how to get the best of both worlds.

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An experimental new silicon (video) that bends like a piece of paper and can be cut like one, too successfully packs big solar tech into thin, flexible material. The benefits are numerous, among them lowering the cost of solar power.

The key to making this thin material work for solar power is etching the surface with a nanostructure design that acts like “a hall of mirrors,” trapping photons inside for as long as possible, according to Stanford University professors Mark Brongersma, Shanhui Fan and associate professor Yi Cui. Their recent review article in Nature Materials (abstract) looks at the latest ultrathin solar cell advancements.

“We are seeing systems that use one-one hundredth as much photovoltaic material as today’s solar cells while getting 60 percent to 70 percent of the electrical output,” Brongersma said in a Stanford news article about the research.

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Yi Cui’s experimental material is 10 micrometers thick. To give you an idea, solar cells manufactured now contain layers that are 150 to 300 micrometers — only as thick as a few human hairs. Cui’s flexible silicon also contains photon-trapping nanostructures. While it’s still in development, he told the university that the light-to-energy conversion is nearing that of rigid silicon in today’s solar cells.

Thin film solar still has a ways to go before it’s efficient enough to be rolled out like wallpaper, but novel new nanostructures are allowing solar materials to do more inside less.

Photo: Engineers are experimenting with an extremely thin silicon material designed to keep photons inside for as long as possible. Credit: Yi Cui, Stanford University.

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