Inside Extreme Scale Tech|Monday, November 24, 2014
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Nanowires Offer Ray of Hope for Efficient Solar Power 

When someone mentions solar power, the first image that comes to mind is typically a midnight-blue panel that spans an entire rooftop. Whether you deem its angular, geometric aesthetic or not is a matter of taste, but a recent breakthrough in nanowire technology could change the state (and looks) of solar cells as we know it.

The process involves arranging microscopic flecks of gold on a semiconductor background, out of which 1.5-micrometer-tall wires are grown from chemically altered indium-phosphorus compounds. The nanowires are then sheered to a diameter of 180 nanometers and cleaned in a hydrochloric acid bath. The result? A solar cell that converts nearly 14 percent of incoming light into electricity (nearly as much electricity as traditional thin-film solar cells) using only 12 percent of the cell’s surface area.

The process, originally published online in Science and later replicated at Germany’s Fraunhofer Institute for Solar Energy Systems, may pave the way for cheaper, more powerful solar power generators, according to lead researcher Magnus Borgström of Lund University in Sweden.

The success of this novel indium-phosphorus semiconductor – its ability to absorb light provided by the sun (or “band gap”) – may also hold promise for future improvements in the technology. “Now we absorb 71 percent of the light above the band gap and we can certainly increase that,” Borgström says.

The research paper has outlined two ways to make this happen. The first is to achieve a greater degree of control over nanowires and the compounds therein. The second is to build the nanowire cells into multijunction solar cells – compound devices that incorporate various compressed semiconductors in order to maximize light absorption. These cells have already proven to be the most efficient photovoltaics in the world, converting more than 43 percent of sunlight energy into electricity.

Granted, multijunction solar cells are the more expensive photovoltaic devices as well, but nanowire cells could still benefit from this technology if combined with lenses that would concentrate sunlight onto smaller versions of the multijunction cell.

Borgström suspects that once the production process is simplified, nanowire solar cells will be able to stand on their own, stating, “Once large-area structure can be grown, concentration will not be necessary anymore.”

If that’s true, Borgström noted, this technology could lead to even cheaper forms of solar power – so long as the process can be industrialized.

 

Full story at Scientific American

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