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Scientists create first solar cell with over 100 percent quantum efficiency
Researchers over at the National Renewable Energy Lab have reportedly made the first solar cell with an external quantum efficiency over 100 percent. Quantum efficiency relates to the number of electrons-per-second flowing in a solar cell circuit, divided by the number of photons from the energy entering. The NREL team recorded an efficiency topping out at 114 percent, by creating the first working multiple exciton generation (MEG) cell. Using MEG, a single high energy photon can produce more than one electron-hole pair per absorbed photon. The extra efficiency comes from quantum dots 'harvesting' energy that would otherwise be lost as heat. The cell itself uses anti-reflection coating on a transparent conductor, layered with zinc oxide, lead selenide, and gold. NREL scientist Arthur J. Nozik predicted as far back as 2001 that MEG would do the job, but it's taken until now for the concept to leap over from theory. The hope is, of course, that this will lead to more competitively priced solar power, fueling the transport of the future.
New solar cell efficiency record (barely) achieved at 40.8%
Just under two years ago, researchers at Boeing-Spectrolab managed to achieve 40.7% solar cell efficiency. Two years later, scientists at the US Department of Energy's National Renewable Energy Laboratory have demonstrated their nerve by trumpeting an all new world record... one that's 0.1% points better than the last. Yes, your new record now sits at 40.8% -- tremendous progress, wouldn't you say? Looking outside of the numbers, you'll find that these cells differ "significantly" from the prior record holders, which enable them to be thinner, lighter, cheaper and altogether swanker. That's it for now folks -- come back in a couple years, we hear 40.9% is just around the bend.[Via CNET]
