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Researchers believe nanowires have potential to 'revolutionise' solar energy

08 April 2013

Capture up to twelve times more light to produce more energy? Nanowires are apparently capable of this - and surpass expectations on solar energy production.

Imagine a solar panel more efficient than today’s best solar panels, but using 10,000 times less material. This is what Ecole Polytechnique Fédérale de Lausanne (EPFL) researchers expect given recent work with tiny filaments called nanowires. Solar technology integrating nanowires could capture large quantities of light and produce energy with incredible efficiency at a much lower cost. This technology is possibly the future for powering microchips and the basis for a new generation of solar panels.
Despite their size, nanowires have tremendous potential for energy production. “These nanowires capture much more light than expected,” says Anna Fontcuberta i Morral about her research (now published in the journal, Nature Photonics).
When equipped with the right electronic properties, the nanowire becomes a tiny solar cell, transforming sunlight into electric current. Anna Fontcuberta i Morral and her team built a nanowire solar cell out of gallium arsenide, a material which is better at converting light into power than silicon. They found that it actually collects twelve times more light than a conventional flat solar cell, and more light means more energy.
The vertically aligned nanowires essentially act like very efficient light funnels. Even though the nanowire is only a few hundred nanometers in diameter, it absorbs light as though it were 12 times bigger. In other words, it has a greater field of vision than expected.
Fontcuberta’s prototype is already almost 10 percent more efficient at transforming light into power than that theoretically allowed for conventional single material solar panels. Furthermore, optimising the dimensions of the nanowire, improving the quality of the gallium arsenide and using better electrical contacts to extract the current could increase the prototype’s efficiency.
Arrays of nanowire solar cells offer new prospects for energy production. This study suggests that an array of nanowires may attain 33 percent efficiency, whereas commercial (flat) solar panels are now only up to 20 percent efficient.

Also, arrays of nanowires would use at least 10,000 times less gallium arsenide. Translating this into dollars for gallium arsenide, the cost would only be $10 per square meter instead of $100,000.
The nanowires can also be mounted on a variety of substrates, be it lightweight, flexible or designed to withstand the harshest of conditions.

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