• Stanford University's all-carbon solar cell

    Credit: Mark Shwartz

    Stanford University's all-carbon solar cell

The constantly evolving field of renewable energy has witnessed significant innovations in the last few years—from artificial photosynthesis to algae-powered solar collectors. A recent announcement by Stanford University heralds yet another noteworthy development, in the form of all-carbon solar cells. 

At first, the news that Stanford chemical engineers have devised a better alternative to the materials used in conventional photovoltaic devices sounds unconvincing. Although carbon is a pervasive element, so is silicon—which may be found in 90 percent of the minerals that comprise the earth's crust, and which is the base semiconducting material of standard photovoltaic devices.

But the scientists are not proposing that carbon replace silicon, but rather rare materials such as indium that are used for electrodes in thin-film solar cells. "Materials like indium are scarce and becoming more expensive as the demand for solar cells, touchscreen panels and other electronic devices grows," said Stanford professor Zhenan Bao in a university press release. "Carbon, on the other hand, is low cost and Earth-abundant."

Unlike inflexible solar rooftop panels, the researchers' thin-film prototype—which utilizes an active layer of graphene and carbon nanotubes—is made from a solution that may be used to coat a variety of surfaces. "Perhaps in the future we can look at alternative markets where flexible carbon solar cells are coated on the surface of buildings, on windows or on cars to generate electricity," Bao said.

Although the all-carbon prototype cell has an efficiency of only one percent, the scientists are optimistic about the advancement of the technology. According to Bao, "We clearly have a long way to go on efficiency. But with better materials and better processing techniques, we expect that the efficiency will go up quite dramatically."

Blaine Brownell is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.