Green Technology Spotlight: Solar Cells Made Completely From Carbon

Stanford University researchers have built a solar cell made completely from carbon, which will make solar much cheaper to manufacture and easy to install.

It would be painted onto a roof as a coating, giving it the "potential to deliver high performance at a low cost," says chemical engineering Professor Zhenan Bao. It could also be painted on the surface of buildings, windows and cars.

And it would be manufactured using simple coating methods that don’t require expensive tools and machines. It also would eliminate expensive and increasingly scarce materials like indium. "Carbon is low cost and Earth-abundant," says Bao.

Carbon also absorbs a lot of solar energy and has extraordinary electrical conductivity, she says.

Bao and her colleagues used sheets of carbon just one atom thick and single-walled carbon nanotubes that are 10,000 times narrower than a human hair.

The research team has filed a patent for the device. "Other groups have reported making all-carbon solar cells, but they were referring to just the active layer in the middle, not the electrodes," says Stanford graduate student Michael Vosgueritchian.

There’s a long way to go on conversion efficiency, which is less than 1% is the lab now, because it primarily absorbs near-infrared wavelengths of light. That should go up quite dramatically with better materials and better processing techniques, says Bao. 

"Materials made of carbon are very robust," she says. "They remain stable in air temperatures of nearly 1,100 degrees Fahrenheit." The ability of carbon solar cells to out-perform conventional devices under extreme conditions is a distinct advantage. 

The research is published in the Oct. 31 online edition of the journal ACS Nano:

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