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21 May 2010

Solar cells sliced and diced

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Peel-and-stamp technique could pave the way for more efficient semiconductors

An alternative method of making light-sensitive semiconductors could lead to high-efficiency solar cells, better night-vision cameras and a host of other applications, according to research published in this week's issue of Nature.

A team led by John Rogers, a materials scientist at the University of Illinois at Urbana-Champaign, has developed a potentially cost-effective technique to produce microchips made of the semiconductor gallium arsenide, which responds well to light. A transfer-printing technique is used to peel and print thin layers of the semiconductor onto glass or plastic, which by overcoming a long-standing problem in gallium arsenide manufacturing could transform the solar-cell industry.

Silicon is the workhorse of the modern semiconductor industry and is used in everything from solar cells to digital cameras. But for decades, scientists have known that when it comes to capturing light, there are better materials out there. Certain types of semiconductors can absorb light much better than silicon, so make better solar cells and infrared-detection devices.

Gallium arsenide is one of the most studied silicon alternatives. It can theoretically convert about 40% of incident solar radiation to electricity, making it twice as effective as silicon. Its efficiency makes gallium arsenide the material of choice for building solar cells for spacecraft.

But like its best applications, the price of gallium arsenide is sky-high. According to Rogers, this is partly because high-quality wafers of gallium arsenide must be grown in carefully controlled chambers. Once grown, the thick wafers are typically sliced up, but only their surfaces are used. Much of the costly material is essentially wasted, says Rogers.

(Nature News)

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