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Counterintuitive “LED-type” solar cell breaks efficiency record

Counterintuitive “LED-type” so...
The record-breaking Alta Devices solar cell (Photo: Joe Foster, Alta Devices)
The record-breaking Alta Devices solar cell (Photo: Joe Foster, Alta Devices)
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Eli Yablonovitch and Owen Miller, who worked out the theory for the new solar cell (Photo: Eli Yablonovitch)
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Eli Yablonovitch and Owen Miller, who worked out the theory for the new solar cell (Photo: Eli Yablonovitch)
The record-breaking Alta Devices solar cell (Photo: Joe Foster, Alta Devices)
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The record-breaking Alta Devices solar cell (Photo: Joe Foster, Alta Devices)

When you think of a solar cell, you probably think of something designed to absorb as much sunlight as possible. What you probably don't think of is something that is also capable of emitting light. Nonetheless, that’s exactly what a new prototype device designed more like an LED does, and it recently set an efficiency record for flat-plate single junction solar cells.

The cell was created by Alta Devices, a California-based company co-founded by University of California, Berkeley professor of electrical engineering Eli Yablonovitch. Together with graduate student Owen Miller, he worked out a mathematical principle which states that “the better a solar cell is at emitting photons, the higher its voltage and the greater the efficiency it can produce.”

Eli Yablonovitch and Owen Miller, who worked out the theory for the new solar cell (Photo: Eli Yablonovitch)
Eli Yablonovitch and Owen Miller, who worked out the theory for the new solar cell (Photo: Eli Yablonovitch)

The prototype cell incorporates a gallium arsenide semiconductor. Electrons within that material are knocked loose to flow freely by the energy of photons in sunlight. As the electrons are knocked loose by the existing photons, other photons are generated in the process.

So far, that’s the same principle that’s at work in most conventional solar cells. However, the prototype cell is designed to let these new photons escape as easily as possible (in part, via a highly-reflective rear mirror surface), which in turn raises the voltage that it is able to produce.

The technology allowed the prototype to achieve an efficiency of 28.3%, which broke the previous record of 26%. Yablonovitch hopes that researchers building on his work may be able to achieve a figure of 30% within a few years.

Although the record-breaking device is a flat-plate single junction cell (meaning it is only capable of absorbing light waves within a given frequency), the principle it uses is said to apply to all types of solar cells.

Source: The Optical Society

21 comments
S Michael
When are people going to stop announcing vapor-ware and produce something that the public can buy.
bio-power jeff
s Michael I think this was just a research finding, not an actual product.
RicardoTheron
Yablonovitch is not a vapor-ware seller, he is a very sound physicist who has already published several fundamental papers in optics/photovoltaics. Maybe some of you have heard about the 4n^2 law, which states that the maximum energy density one could ever achieve in an optical medium is proportional to the square of the index of refraction of the medium (n^2). Well, this is one of Yablonovitch's contribution to solar cells. Just to say, even if the "LED-type" seems counterintuitive, I would not be surprised that Yablonovitch has just made a new beautiful contribution to our understanding of the photovoltaic conversion phenomena.
Francois Parent
What I think S Michael means is that we keep reading about higher and higher efficiency products but this does not translate in affordable products we can use.
Iván Imhof
There is always a time gap before a result of a scientific research can be applied in mass production. There are lot of technological problems to solve. Especially, if some industry leaders have another interests.
MasterG
Still waiting for my mr. Fusion, this does however greatly enhance the understanding of photovoltaics. I pray i can hand my son a world of tron like power so he can concentrate on better things than survival
mikewax
it seems like every month we hear of some new development in PV technology, higher efficiency, cheaper manufacturing, less costly materials, etc.... current PV products have an efficiency of... what, 20%? i think it'll need at least another 10% before solar power really takes off, but that probably will not be for another ten years.
Mirmillion
Nice stuff. While other groups are trying to squeeze an extra 2% from Mono-C solar cells, this guy is breaking new ground. The nay-sayers will be left with behind with their heads in the sand and their certainty intact.
Brent Eagleson
... regardless of the nay-sayers, I want to thank you Professor Yablonovitch and Owen Miller for your success, on behalf of my grandson... truly a great achievement. Pure genius IMHO
Gregg Eshelman
Suddenly! It's 1940! "Let there be light" by Robert A. Heinlein, writing as Lyle Monroe. RAH used many pen names so it wouldn't look like he was writing nearly half the stories in the pulp magazines - which he was. ;) http://en.wikipedia.org/wiki/Let_There_Be_Light_(short_story) It's a story about solid-state light emitting panels that can also convert light into electricity. Yablonovitch-Miller doesn't have the same ring to it as Douglas-Martin. ;)