December 28, 2012

NBC News

Record set in solar cell efficiency with the light of a thousand suns

Scientists at the U.S. Department of Energy have created a solar cell that can convert 44 percent of sunlight hitting it into electrical energy, setting a new record for solar cell efficiency. But it was only achieved by multiplying the power of the sun by nearly 1,000.

The ongoing research is being done at the III-V Multijunction Photovoltaics group at the Department of Energy's National Renewable Energy Laboratory, where the previous record of 43.5 percent was set. So while it's not a huge leap in efficiency, it's still a record.

The researchers achieve these high efficiencies by stacking multiple "junctions" into a single solar cell, each of which absorbs light at a slightly different wavelength. The "III-IV" in the name refers to the fact that the elements used come from the third and fifth columns of the periodic table.

A new material with many desirable properties was discovered by accident (gallium arsenide diluted with nitrogen), but proved extremely difficult to manufacture. Researchers needed to use a technique called molecular beam epitaxy to minimize impurities in the material — but no one in the world could do it.

Solar Junction, a company started by researchers from Stanford University, decided to take up the challenge. With a few million dollars in funding, Solar Junction and NREL managed to make the new process work. The result was the "SJ3" cell, which has been breaking records ever since.

To read the full article, visit: