Carbon Emerges as New Solar Power Material

Carbon-based photovoltaic devices might one day replace silicon solar cells

Flickr/Jeremy Levine

Researchers are investigating how carbon can harness the sun's light, potentially replacing more expensive and toxic materials used in conventional photovoltaic technologies.

Now a team at Stanford University has developed a solar cell whose components are made solely from carbon. The scientists published their findings last month in the journal ACS Nano.

"We were interested in forming basically a new type of solar cell in which the materials being used are all carbon materials," said Michael Vosgueritchian, a doctoral student in chemical engineering at Stanford and a co-author.

He explained that carbon materials have several traits that make them appealing to energy developers. "There's no fear of running out of carbon," Vosgueritchian said. "These materials, since they are nanomaterials, they are solution processable. They can be deposited by spraying and coating without high temperatures or vacuums."

Contrast this with typical silicon-based solar panels: Manufacturers need very pure silicon and have to heat it to high temperatures. The devices' electrodes often consist of expensive, rare or dangerous elements like cadmium, tellurium and indium. When a photovoltaic panel wears out, these chemicals also create a disposal hazard.

Working under Zhenan Bao at Stanford, Vosgueritchian said, the research team used several flavors of carbon to construct its device. Graphene, a carbon structure in which the atoms lie in thin sheets of hexagons, formed the anode.

If graphene is rolled into a cylinder, it becomes a carbon nanotube. Nanotubes made up part of the device's active layer, which converts light to electricity. On top was a layer of 60-carbon fullerenes, soccer-ball-shaped arrangements of atoms. The final layer was a cathode composed of nanotubes.

'A long way to go' before practical use Michael Strano, a professor of chemical engineering at the Massachusetts Institute of Technology, explained that this junction between nanotubes and fullerenes "represents a fundamentally new kind of solar cell." His team developed a device using this system and published its work in Advanced Materials in June.

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Carbon Emerges as New Solar Power Material

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