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US and Italian team develop world's first all-carbon solar cell

MIT create breakthrough carbon nanotube PV cell to harness 40% unused solar energy

The all-carbon cell will be a breakthrough for solar cell technology

US researchers have developed what is claimed to be the world’s first all-carbon solar cell. With the support of Italian company Eni, The Massachusetts Institute of Technology (MIT) in the US has developed the cell, which could harness 40 per cent of unused solar energy.
About 40 per cent of the solar energy reaching the Earth’s surface lies in the near-infrared region of the spectrum - energy that conventional silicon-based solar cells are unable to harness. But the solar cell could tap into that unused energy, opening up the possibility of combination solar cells - incorporating both traditional silicon-based cells and the new all-carbon cells - that could make use of almost the entire range of sunlight’s energy.

“This is the first all-carbon photovoltaic cell,” said Michael Strano, the Charles and Hilda Roddey professor of chemical engineering at MIT. “It’s a fundamentally new kind of photovoltaic cell.”

The new cell is made of two exotic forms of carbon: carbon nanotubes and C60, otherwise known as buckyballs.

“It has only been within the last few years or so that it has been possible to hand someone a vial of just one type of carbon nanotube,” Strano said.

In order for the new solar cells to work, the nanotubes have to be very pure, and of a uniform type: single-walled, and all of just one of nanotubes’ two possible symmetrical configurations.

The MIT said other groups have made PV cells using carbon nanotubes, but only by using a layer of polymer to hold the nanotubes in position and collect the electrons knocked loose when they absorb sunlight. But that combination adds extra steps to the production process, and requires extra coatings to prevent degradation with exposure to air. The new all-carbon PV cell appears to be stable in air, Strano says.

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.

“We are very much on the path to making very high efficiency near-infrared solar cells,” the MIT said.