Carbon Nanotubes Serve as Funnel for Photons on Solar Panels

Nothing excites the imagination of the general public or researchers in the area of alternative energy like solar power does. You can explain until you’re blue in the face how wind power is cheaper per Kwh than solar, or how nanotech is really having an impact now on saving energy as opposed to generating it.

But it all hardly seems to matter. People want to know how nanotech is going to enable solar power. The latest news item comes out of MIT where researchers have formed carbon nanotubes into a kind of antenna that focuses photons onto photovoltaic cells and reportedly concentrates solar energy 100 times more than a regular cell.

According to Michael Strano, the leader of the research team and Charles and Hilda Roddey Associate Professor of Chemical Engineering at MIT, this development could result in smaller 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 in the article.

The work was originally published in the Sept. 12 online edition of the journal Nature Materials.

The antennas are made of about 30 billion carbon nanotubes and resemble a fibrous strand with dimensions of 10 micrometers long and four micrometers thick. The fiber has different bandgaps. The inner layer of the fiber has a small bandgap while the outerlayer have a higher bandbap. So when photons hit the antenna all the excitons flow to the center of the fiber thereby concentrating them.

While this is all very far off from even a full-fledged prototype since the researchers have not yet built a photovoltaic cell that could use the antenna, it seems that commercial considerations are already being taken into account with concerns about the price per pound of single-walled carbon nanotubes being discussed.

One would think that a discussion of economic issues like price of raw materials and phrases like “100 times” better than existing technologies would interest funding types. But likely they see 10 years before a ROI and myriad competing technologies and shrug.