All-Carbon Solar Cells Capture Infrared Light

© Rishabh Jain et al
Atomic-force microscope image of a layer of single-walled carbon nanotubes deposited on a silicon surface.

MIT researchers have made a pretty big breakthrough in solar cell technology -- a solar cell that is capable of harnessing light in the infrared region of the spectrum -- something that no current solar cells are capable of doing. This new technology could be used to create compound solar cells that could utilize almost the entire range of sunlight.

The new cell is the first all-carbon solar cell and is made up of two types of carbon: carbon nanotubes and C60, also known as buckyballs. Only recent advancements in the production of carbon nanotubes that allow for very pure nanotubes to be placed in a perfectly uniform configuration have made this solar cell possible. It's a true example of breakthroughs in one area of technology leading to breakthroughs in another.

MIT News reports:

The carbon-based cell is most effective at capturing sunlight in the near-infrared region. Because the material is transparent to visible light, such cells could be overlaid on conventional solar cells, creating a tandem device that could harness most of the energy of sunlight. The carbon cells will need refining...So far, the early proof-of-concept devices have an energy-conversion efficiency of only about 0.1 percent.

But while the system requires further research and fine-tuning, “we are very much on the path to making very high efficiency near-infrared solar cells,” says Rishabh Jain, a graduate student who was lead author of the paper.

Because they are made of nanoscale materials, the cells would require only small amounts of the highly purified carbon and they would be very lightweight. Their makeup of nanotubes also means that the researchers know exactly where to make improvements to increase efficiency, like coming up with ways to have better control over the exact shape and thickness of the layers of material they produce.

But this new cell doesn't need a super high efficiency to be a huge gain for solar technology. Since the near-infrared part of the solar spectrum is totally unused by current silicon solar cells, senior author of the paper on the technology Michael Strano points out that even a low-efficiency cell that works in that region could be worthwhile as long as its cost is low. “If you could harness even a portion of the near-infrared spectrum, it adds value,” he says.

Tags: Nanotechnology | Solar Technology

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