The solar cell that also shines: Luminescent 'LED-type' design breaks efficiency record

[Dead_Parrot]

Research to be presented at the Conference on Lasers and Electro Optics illuminates 50-year mystery

WASHINGTON, April 19—To produce the maximum amount of energy, solar cells are designed to absorb as much light from the Sun as possible. Now researchers from the University of California, Berkeley, have suggested – and demonstrated – a counterintuitive concept: solar cells should be designed to be more like LEDs, able to emit light as well as absorb it. The Berkeley team will present its findings at the Conference on Lasers and Electro Optics (CLEO: 2012), to be held May 6-11 in San Jose, Calif.

"What we demonstrated is that the better a solar cell is at emitting photons, the higher its voltage and the greater the efficiency it can produce," says Eli Yablonovitch, principal researcher and UC Berkeley professor of electrical engineering.

Since 1961, scientists have known that, under ideal conditions, there is a limit to the amount of electrical energy that can be harvested from sunlight hitting a typical solar cell. This absolute limit is, theoretically, about 33.5 percent. That means that at most 33.5 percent of the energy from incoming photons will be absorbed and converted into useful electrical energy.

Yet for five decades, researchers were unable to come close to achieving this efficiency: as of 2010, the highest anyone had come was just more than 26 percent. (This is for flat-plate, "single junction" solar cells, which absorb light waves above a specific frequency. "Multi-junction" cells, which have multiple layers and absorb multiple frequencies, are able to achieve higher efficiencies.)

More: http://www.eurekalert.org/pub_releases/2012-04/osoa-tsc041912.php
CLEO: http://www.cleoconference.org/