New method to make gallium arsenide solar cells

May 20, 2010 by Lin Edwards report
Image of a printed GaAs solar cell with a size ~10 x 10 mm2 on a glass substrate, with simple, metal grid contacts. Image copyright: Nature, DOI:doi:10.1038/nature09054

( -- A new "transfer-printing" method of making light-sensitive semiconductors could make solar cells, night-vision cameras, and a range of other devices much more efficient, and could transform the solar industry.

Scientists at the University of Illinois at Urbana-Champaign have developed a new and cheaper way of producing microchips of (GaAs), a compound semiconductor that responds to light. Gallium arsenide is about twice as effective as silicon in converting incident solar radiation to light, with a theoretical conversion rate of up to 40 percent, and has for that reason been used in solar cells in space crafts.

The problem with GaAs is its expense and the need for wafers to be grown in precisely controlled conditions. The wafers are sliced for use, but only the surfaces are used and the rest is essentially wasted. Now the Illinois research team, led by materials scientist John Rogers, has developed an alternative and potentially much more cost-effective technique involving growing stacks of layers of GaAs alternating with aluminum arsenide (AlAs).

When the stack is complete, the scientists then chemically etch away the AlAs layers using hydrofluoric acid, leaving the films of GaAs, which they then peel off and stamp onto another substrate such as glass, silicon, or plastic using a silicon-based soft rubber stamp. Rogers and his colleagues have been working on perfecting the technique for around ten years.

Semiconductor manufacturing technique holds promise for solar energy
This is a flexible array of gallium arsenide solar cells. Gallium arsenide and other compound semiconductors are more efficient than the more commonly used silicon. Credit: John Rogers

They have learned that if they press the stamp on the stack and lift it quickly it picks up only the top film. They then transfer the GaAs to the substrate by stamping it onto the surface and peeling the stamp back slowly. They could then build the devices such as , semiconductor field effect transistors and , and near-infrared imaging devices on the substrates. The method yields large quantities of high quality GaAs films, leaving the original wafer for reuse to grow more films.

Using their technique, which is described in the journal Nature, the researchers succeeded in mass-producing tiny solar cells about 500 micrometers in diameter, and they also produced components for mobile phones and infrared-imaging devices.

Rogers said GaAs has a great deal of potential in the future, and the team is now developing commercially viable that will be able to generate electricity for about $1 per watt.

Semiconductor manufacturing technique holds promise for solar energy
A pile of gallium arsenide solar cells is manufactured in stacks and then peeled apart layer by layer. They can be integrated into a number of electronic devices. Credit: John Rogers

Explore further: Unexpected new mechanism reveals how molecules become trapped in ice

More information: Jongseung Yoon, GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies, Nature, Volume: 465, Pages: 329-333, Date published: 20 May 2010, DOI:doi:10.1038/nature09054

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5 / 5 (2) May 20, 2010
I knew when I clicked on it that the article would have nothing to do with solar cell production because this is PhysOrg.

I don't understand you would choose a title that intimates an article about some novel production of gallium arsenide solar cells when the article is actually speaking to gallium arsenide production.

How about "New method to make gallium arsenide supercomputers on a chip!" makes as much sense.
1 / 5 (1) May 20, 2010
I love solar power. Saves so much on the electric bill!
2 / 5 (2) May 20, 2010
Given the inaccurate journalism, this approach does look promising.
May 23, 2010
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