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Quantum Dots Boost Solar-Cell Efficiency, Cut Costs, NREL Says

Solar cells may one day use microscopic chunks of semiconductors known as quantum dots to produce more power and cut production costs, according to an article to be published Dec. 16 in the journal Science.

Conventional solar cells struggle to convert high-energy photons in sunlight into electricity, said Matt Beard, a senior scientist at the National Renewable Energy Laboratory and one of the article’s authors.

Quantum dots, pieces of semiconductor materials measuring 2 nanometers, or 2 billionths of a meter, let cells convert more photons into electricity. The technique may boost conversion efficiency by as much as 30 percent, he said.

“Using quantum dots as your absorber material, you can better convert that high-photon electricity,” Beard said in a telephone interview from Golden, Colorado.

The semiconductor materials used to make solar cells now must be produced at high temperature, about 600 degrees Celsius (1,112 degrees Fahrenheit), Beard said. Quantum dot materials can be made at about 200 degrees Celsius and consume less energy, reducing manufacturing costs.

The NREL test used solar cells measuring 1 square centimeter. The technology is not commercially viable now and it will likely be at least five years before the quantum-dot technology may be produced in panels large enough for rooftops, Beard said.

“There still needs to be a lot of work in improving the overall conversion efficiency for the solar cell,” Beard said. “We’re not there yet.”

Richard Swanson, co-founder and president emeritus of SunPower Corp., the second-largest U.S. solar manufacturer, said in an e-mailed statement that given the long development cycle, it’s premature to evaluate the commercial implications of the technology, “except to cheer on the researchers.”

To contact the reporter on this story: Justin Doom in New York at jdoom1@bloomberg.net

To contact the editor responsible for this story: Reed Landberg at landberg@bloomberg.net

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