MIT Develops New Way to Funnel Solar Energy

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"Concentrated solar energy 100x more than a regular photovoltaic cell."

Using carbon nanotubes (hollow tubes of carbon atoms), MIT chemical engineers have found a way to concentrate solar energy 100 times more than a regular photovoltaic cell. Such nanotubes could form antennas that capture and focus light energy, potentially allowing much smaller and more powerful solar arrays.

"Instead of having your whole roof be a photovoltaic cell, you could have little spots that were tiny photovoltaic cells, with antennas that would drive photons into them," says Michael Strano, associate professor of Chemical Engineering and leader of the research team.

Strano and his students describe their new carbon nanotube antenna, or "solar funnel," in the Sept. 12 online edition of the journal Nature Materials. Lead authors of the paper are postdoctoral associate Jae-Hee Han and graduate student Geraldine Paulus.

Their new antennas might also be useful for any other application that requires light to be concentrated, such as night-vision goggles or telescopes.

Solar panels generate electricity by converting photons into an electric current. Strano's nanotube antenna boosts the number of photons that can be captured and transforms the light into energy that can be funneled into a solar cell.

The antenna consists of a fibrous rope about 10 micrometers long and 4 micrometers thick, containing about 30 million carbon nanotubes. MIT, for the first time, a fiber made of two layers of nanotubes with different electrical properties—specifically different bandgaps.

Therefore, when light energy strikes the material, all of the excitons flow to the center of the fiber, where they are concentrated. Strano and his team have not yet built a photovoltaic device using the antenna, but they plan to. In such a device, the antenna would concentrate photons before the photovoltaic cell converts them to an electrical current. This could be done by constructing the antenna around a core of semiconducting material.

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