Carbon Nanotube 'Light Funnel' Could Make Solar Panels More Efficient

solar nanotubes image

Photo: Patrick Gillooly, MIT
What Can't We Do With Carbon Nanotubes?
MIT researchers have found a way to use carbon nanotubes to concentrate light by about 100x and funnel photons into smaller (thus less expensive) solar panels. "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, the Charles and Hilda Roddey Associate Professor of Chemical Engineering and leader of the research team.
solar nanotubes image

Photo: Geraldine Paulus, MIT

The nanotube funnels/antennas are made of "fibrous rope" about 10 micrometers (millionths of a meter) long and four micrometers thick, containing about 30 million carbon nanotubes. The MIT team built a fiber made of two layers of nanotubes with different electrical properties.

The inner layer of the antenna contains nanotubes with a small bandgap, and nanotubes in the outer layer have a higher bandgap. That's important because excitons like to flow from high to low energy. In this case, that means the excitons in the outer layer flow to the inner layer, where they can exist in a lower (but still excited) energy state.

Therefore, when light energy strikes the material, all of the excitons flow to the center of the fiber, where they are concentrated.

At the rate at which carbon nanotubes are dropping in price (it is forecast that they will soon cost pennies per pound), using them in solar arrays could help drive down the cost of solar power (ie. it will be less expensive to have small solar panels and big carbon nanotube concentrators than just big silicon panels to cover the same surface.

Of course, other types of solar concentrators will compete with this one, so it will remain to be seen if maybe cheaper alternatives can work as well.

Via MIT, Science Daily
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