Sunday, December 23, 2007

More Than One

Small Times is reporting the development of a solar cell that can deliver more than one electron for each photon absorbed.

Researchers at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL), collaborating with Innovalight, Inc., say they have shown that a new and important effect called Multiple Exciton Generation (MEG) occurs efficiently in silicon nanocrystals. MEG results in the formation of more than one electron per absorbed photon.

Silicon is the dominant semiconductor material used in present day solar cells, representing more than 93% of the photovoltaic cell market. Until this discovery, MEG had been reported over the past two years to occur only in nanocrystals (also called quantum dots) of semiconductor materials that are not presently used in commercial solar cells, and which contained environmentally harmful materials (such as lead). The new result opens the door to the potential application of MEG for greatly enhancing the conversion efficiency of solar cells based on silicon because more of the sun's energy is converted to electricity. This is a key step toward making solar energy more cost-competitive with conventional power sources.
This is very helpful except for one minor point. The wavelength of the absorbed light is required to be 420 nm or less. This is in the ultraviolet. There is not a lot of ultraviolet at the earth's surface. The atmosphere absorbs most of it. However, it is a step in the right direction and it will definitely help with solar satellite arrays. There is a lot of ultraviolet available in space.

Cross Posted at Classical Values

1 comment:

LarryD said...

First application: satallites and space probes.

But power sats are a long way off. Even the NSSO paper on Space Based Solar Power acknowledges that cheap orbital access is necessary to make SBSP viable. The NSSO paper talks hopefully of a four decade timeline.

Here's really hoping IEC fusion pans out. We're going to need it to get the cheap orbital capacity needed for SBPS. Although then a lot of the pressure to build a SBPS system goes away.