Wednesday, February 17, 2010

Solar: What Would You Think of a Cell that Can Trap 85% of Available Light?

I've said it a few times, most recently in last month's "Deep Solar Science at Stanford":
Besides the dependence on subsidies the scariest thing about investing in solar is the possibility that some lab in Shenzen or Cambridge (both of 'em) or Cali will come up with something that makes current technology obsolete overnight....
Here's some more lab work, via EurekAlert:

Caltech researchers create highly absorbing, flexible solar cells with silicon wire arrays

Using arrays of long, thin silicon wires embedded in a polymer substrate, a team of scientists from the California Institute of Technology (Caltech) has created a new type of flexible solar cell that enhances the absorption of sunlight and efficiently converts its photons into electrons. The solar cell does all this using only a fraction of the expensive semiconductor materials required by conventional solar cells.

"These solar cells have, for the first time, surpassed the conventional light-trapping limit for absorbing materials," says Harry Atwater, Howard Hughes Professor, professor of applied physics and materials science, and director of Caltech's Resnick Institute, which focuses on sustainability research.

The light-trapping limit of a material refers to how much sunlight it is able to absorb. The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight. "We've surpassed previous optical microstructures developed to trap light," he says.

Atwater and his colleagues—including Nathan Lewis, the George L. Argyros Professor and professor of chemistry at Caltech, and graduate student Michael Kelzenberg—assessed the performance of these arrays in a paper appearing in the February 14 advance online edition of the journal Nature Materials.

Atwater notes that the solar cells' enhanced absorption is "useful absorption."

"Many materials can absorb light quite well but not generate electricity—like, for instance, black paint," he explains. "What's most important in a solar cell is whether that absorption leads to the creation of charge carriers."

The silicon wire arrays created by Atwater and his colleagues are able to convert between 90 and 100 percent of the photons they absorb into electrons—in technical terms, the wires have a near-perfect internal quantum efficiency. "High absorption plus good conversion makes for a high-quality solar cell," says Atwater. "It's an important advance."

The key to the success of these solar cells is their silicon wires, each of which, says Atwater, "is independently a high-efficiency, high-quality solar cell." When brought together in an array, however, they're even more effective, because they interact to increase the cell's ability to absorb light....MORE

HT: FuturePundit whose commenters seem to be reasonably sharp.

There are two areas of knowledge required for the next industrial revolution, this is an example of one of them, materials science at the nano level.

The other is manufacturing science where, in the first industrial revolution, it seemed that half the engineers in the world were Scottish. Who's going to step up this time?