Monday, February 15, 2010

Solar Energy Harvesting Using 1 Percent Of Current Materials

Imagine a world where sunlight can be captured to produce electricity anywhere, on any surface. The makers of thin-film flexible solar cells imagine that world too. But a big problem has been the amount of silicon needed to harvest a little sunshine.

Now, researchers [led by Harry A. Atwater] at Caltech say they’ve designed a device that gets comparable solar absorption while using just one percent of the silicon per unit area that current solar cells need. The work was published in the journal Nature Materials.

The research team tried silicon wire arrays instead of traditional silicon panels. These wires have been shown to do a good job converting sunlight to usable energy on the nanoscale. But the scientists had to create wires a thousand times longer.

Light bounces around within the wires and is eventually absorbed when it hits at the correct angle. But there was a problem: too much light was leaking out. Adding nanoparticles of alumina kept much more of the light scattering until it got absorbed. The result is a system that virtually matches silicon wafer light absorption and may be more efficient at converting light to electricity, while using a tiny fraction of the material.—Cynthia Graber

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Tuesday, July 07, 2009

Light-absorbing nanowires

Light-absorbing nanowires may make better solar panels
BY DAVID ORENSTEIN

A century after German physicist Gustav Mie derived the math to explain why the colors in some stained glass windows look especially resplendent in the sunlight, a team of Stanford engineers has built upon his work to potentially improve a means of harvesting energy from the sun.

In 1907 Mie realized that tiny metal particles in stained glass scattered light in ways that produced beautiful colors. Now, a related interplay between light and matter explains why incredibly thin "nanowires" made of semiconductors like germanium may prove to be effective components for solar cells. Combining Mie's work with more recent theory, the Stanford team has discerned how to tune and improve the light absorption efficiency of the wires. Their research appears in the July 5 online edition of the journal Nature Materials.

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