Solar researcher seeks quantum leap

Arthur Nozik honored for scientific career

A moment of inspiration a decade ago has put National Renewable Energy Laboratory scientist Arthur Nozik in the thick of a global scientific quest that could help solve the world's energy problems.

Nozik's idea - to harness quantum behavior to extract perhaps 50 percent more electricity from a solar cell and make the technology cheaper than today's panels - is now being pursued by researchers worldwide, including those in his own NREL group.

Art Nozik
Arthur Nozik, a senior research fellow at the National Renewable Energy Laboratory in Golden and an adjoint chemistry professor at the University of Colorado, is the lead scientist on a proposal to bring a “Center for Revolutionary Photoconversion” project to the Colorado
Renewable Energy Collaboratory, a cooperation among NREL, CU, Colorado State University and the Colorado School of Mines. Marty Caivano/Daily Camera

Nozik, 71, lives in Boulder. He is one of six NREL research fellows and is a University of Colorado adjoint professor of chemistry.

He joined NREL-predecessor Solar Energy Research Institute a year after President Jimmy Carter launched it in 1977. Ever since, he has worked to make solar panels more efficient.

In December, the Journal of Physical Chemistry honored Nozik's 70th year with a special publication of articles related to his research. NREL scientist Mike Heben was a co-author of the issue.

"He's the monk that's retained the flame over the life of this laboratory, and it's had a radiating effect all over the country and the world," Heben said. "He's a substantial person in this area, and he has been for a long time."

Nozik had planned on taking it easy when he reached his seventies. It hasn't happened.

"I've got too much momentum," Nozik said. "It's hard to stop right now."

Nozik's notion is conceptually simple and scientifically daunting. Silicon solar cells being installed on rooftops today work by converting one photon of light energy into a single electron, the basic unit of electricity. But all photons are not created equal, and therein lies opportunity.

Sunlight consists of a mishmash of light with varying amounts of energy. Nozik 's idea is to find "quantum dots" or even designer chemicals that release two or perhaps even three electrons when a potent photon strikes - rather than spitting out a single electron and losing the balance as waste heat.

Today's best mass-production solar cells convert about 22 percent of sunlight into electricity in the laboratory and about half that much by the time they're installed and operating on a roof, Nozik said. The laws of physics limit them to 31 percent efficiency. Nozik's two-for-one deal would raise that limit to 42 percent, he said.

"That work is really important. That work, to me, is earth-shattering," said Brad Collins, executive director of the American Solar Energy Society in Boulder.

A system using quantum dots - hockey pucks a few billionths of a meter across - could be cheaper to make than sheets consisting of single silicon crystals, which cost $15,000 or more to install on a neighborhood rooftop.

"The ultimate idea is to make solar paint," Nozik said. "You just paint your wall or your roof."

Before Dutch Boy and Glidden start cutting electric bills, there are major hurdles.

NREL scientist Matthew Beard, who works in Nozik 's Chemical Science Basic Research Group lab, said the team has managed to generate multiple electrons with single photons, as have other groups. The big problem, he said, is getting the energy out of the dots.

He and others on Nozik's 10-person team have been using ultrafast lasers to understand how different types of quantum dots react to different wavelengths of light. It is a painstaking process.

But what Nozik calls "high-risk, high-payoff research" is what the country needs if photovoltaic systems are to be competitive with electricity derived from wind or fossil fuel, and, eventually, liquid fuels such as gasoline, he said. Electricity from commercial photovoltaic systems still costs about 30 cents per kilowatt hour once financing and other costs are figured in, or about five times that of new coal or wind. Gasoline, at $2.25 per gallon, is the equivalent of 4 cents per kilowatt hour, he said.

Solar panels have already fallen from $3.65 per kilowatt hour in 1976. But NREL researchers say the world can't wait 20 years for the current generation to be competitive with fossil fuels.

Global energy demands are expected to roughly double by 2030. It would take more than 14,000 new nuclear plants to produce so much. Fossil fuels as burned today emit heat-trapping carbon dioxide. Energy researchers say solar energy is the only option with a chance of replacing coal, oil and gas into the latter half of the century.

"Climate change is really such a serious problem, and renewables have to play a role," Nozik said. "We don't have that much time."