While the sun beats down a lot of light and energy on earth, we can only see a tiny percentage of it. All that light we can’t see is the new frontier for solar power. Today’s photovoltaics, like our eyes, are designed for the visible spectrum: a good chunk of the sun’s energy passes by unnoticed (except as the occasional sunburn).
But that’s inefficient since a standard solar cell will capture, and convert, only a fraction of the solar energy that reaches its surface. The near-infrared part of the solar spectrum—about one-third of what hits the panel—is essentially wasted. Capturing this energy, even at low efficiencies, could prove worthwhile by significantly boosting energy production, as long as the new panels are cheap to make.
Researchers at MIT have now done that. Their first "all-carbon" solar cells, reported in Advance Materials this month, uses carbon instead of silicon as the primary material. The cells work by employing carbon nanotubes and C60—also known as buckyballs—to turn infrared light into an electric current.
Affordable large-scale production of purified carbon nanotubes is only now becoming a scientific reality. But with further refinements, carbon-based infrared solar panels could spread throughout the industry (and on to many surfaces). Since the material is transparent to visible light, it can overlay conventional solar cells or other materials. "It’s very much a model system and other groups with help increase the efficiency," says Rishabh Jain, a graduate student and a lead author of the study.
And MIT’s carbon solar cells are not alone in their pursuit of infrared. Researchers have started harnessing such solar energy with dyes and spray-on nano-materials as well.