15 September 2010

Carbon Nanotubes Concentrate Solar Energy Better Than Photovoltaic Cells

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Nanotubes concentrate solar energy 100 times more and can be used for a variety of applications
MIT chemical engineers have developed a way to concentrate solar energy 100 times more than a traditional photovoltaic cell through the use of carbon nanotubes.

Jae-Hee Han, postdoctoral associate and lead author; Geraldine Paulus, graduate student and lead author; and Michael Strano, leader of the research team have devised a way to use carbon nanotubes (hollow tubes of carbon atoms) to form antennas that capture and focus light energy, resulting in more powerful and smaller solar arrays.

"Instead of having your whole roof be a photovoltaic cell, you could have little spots that were tiny photovoltaic cells, with antenna's that would drive photons into them," said Strano.

Traditional solar panels convert photons into an electric current to generate electricity, but with the use of the nanotube antenna, the number of photons being captured increases and light is transformed into energy that can be funneled into the solar cell.

These new antenna's are called "solar funnels," and can be used in various other applications such as telescopes or night-vision goggles, where light needs to be concentrated. They contain a fibrous rope that is 10 micrometers long and four micrometers thick, and consist of 30 million carbon nanotubes. The fiber is made up of two layers of nanotubes with different bandgaps, which is the difference in energy levels between an electron and the hole it leaves behind. When photons strike a surface, this excites the electron to a higher degree depending on the material, and interactions between the electron and the hole it leaves behind is an exciton.


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