Engineering a quantum leap in solar power

Take a look at a solar panel on a sunny Colorado day and, if you’re like most people, you won’t see much more than a blinding glare. Mark Lusk sees wasted opportunity.

“I see that glare and feel how hot the panels on my roof get and say, ‘What a waste! We’re losing energy!’” says Lusk, a Mines physics professor and solar energy researcher, who admits to checking out his panels and their energy output more than most. On a clear day, he explains, only a fraction of the photons hitting the photovoltaic cells on his roof are converted into electricity—the rest bounce off as light or are lost as heat. On a cloudy day, or as dusk approaches, the long-wavelength, low-energy particles of light are scarcely enough to produce any juice at all. On average, just 20 percent of the sun’s rays actually get converted to energy in a contemporary solar cell.

“In terms of efficiency, there is a lot of room for improvement up there,” he says.

Fueled by a six-year, $12 million grant from the National Science Foundation, Lusk and his colleagues at the Renewable Energy Materials Research Science and Engineering Center (REMRSEC) have spent the last four years working to improve that efficiency via a complex merging of nanotechnology, quantum physics and computational wizardry known as “exciton engineering.”

The nascent and controversial field hinges on the manipulation of “excitons”—the combination of an excited electron and the hole from which it is dislodged by an incoming photon. In conventional photovoltaic cells, the exchange is generally one-for-one; upon impact, a photon creates an exciton, which sends a highly energized electron racing into an electrical circuit.

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