The all-carbon cell developed by Professor Míchael Strano and his team at MIT (Massachusetts Institute of Technology) can tap into the unused energy in the near-infrared region of the light spectrum. Conventional silicon based cells are incapable of harnessing this wavelength potential, according to the researcher.
By combining silicon solar cells and the all-carbon cells almost the entire range of the light spectrum can be captured. The material is transparent to visible light, hence a tandem device can be created with conventional cells via an overlay. Nevertheless, as Strano says, the carbon cells are still in need of refinement.
Efficiency issues are still present as is typical for new solar cell materials. But this is something the scientists are working on. Sources of inefficiencies have already been identified by the team in the case of the carbon cell. "Its pretty clear to us the kinds of things that need to happen to increase the efficiency," graduate student Rishabh Jain says.
One area the MIT researchers are now exploring is more precise control over the exact shape and thickness of the layers of material they produce, he says. With that said, it will probably take some years before mass production steps can be part of the plan.
"It’s a fundamentally new kind of photovoltaic cell," says Strano who is also the senior author of a paper describing the new device that was published this week in the journal Advanced Materials. The research combined two exotic forms of carbon: carbon nanotubes and C60 which is also 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 addss.
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.
Michael Arnold, an assistant professor of materials science and engineering at the University of Wisconsin at Madison who was not involved in this research, says, "Carbon nanotubes offer tantalizing possibilities for increasing the efficiency of solar cells and are kind of like photovoltaic polymers on steroids." This work, he adds, "is exciting because it demonstrates photovoltaic power conversion using an active layer that is entirely made from carbon."