Cheaper Gallium Arsenide Deposition, 37% Solar

Compared to silicon, semiconductors like gallium arsenide can be made into solar cells that convert more sunlight into electricity and transistors that are faster than their silicon counterparts. But devices made from these materials are expensive.

Now a new method for making large-area devices from gallium arsenide promises to bring down costs by eliminating manufacturing steps and wasting less materials. Researchers have used the method to make high-performance image sensors, transistors, and solar cells. Semprius, a Durham, NC, company, is using it to make solar modules that should be on the market by the end of the year.

Gallium arsenide solar cells convert twice as much of the energy in sunlight into electricity compared to silicon cells, says John Rogers, professor of materials science and engineering at the University of Illinois at Urbana-Champaign, who led the research. Gallium arsenide is also being eyed by microchip manufacturers such as Intel as a potential replacement for silicon.

The problem with gallium arsenide, however, is its price tag. To make a gallium arsenide solar panel today, manufacturers grow a semiconductor crystal on an expensive template in a high-vacuum, high-temperature chamber. The gallium arsenide is then diced into thin pieces, assembled, and bonded. This process destroys the underlying template, which is necessary to create a high-quality crystal. And making only a single layer of gallium arsenide at a time is inefficient--it takes more time to load and unload the vacuum chamber than it does to grow the crystal.

To address the problem, Rogers developed a method for growing multiple layers of devices at one time, and a way to release them from the substrate without destroying it. "Once the substrate is in the chamber at the right temperature, we grow a multilayer stack," explains Rogers. The stack alternates a device layer with a sacrificial layer. After all the layers are put down, the stack is etched in a chemical bath that eats away at the sacrificial layer, made of aluminum arsenide, releasing thin rectangular films of gallium arsenide. As the gallium arsenide films are released, they're picked up and placed on a substrate.

http://www.technologyreview.com/computing/25363/

Advances in Thin Film Technologies for MEMS and Solar

Advances in thin films technologies are transforming traditional manufacturing processes and whetting the appetite of industry.Multiple new techniques in thin films technology are vying for supremacy in two rapidly growing sectors—microelectromechanical systems (MEMS) and highly-efficient photovoltaic systems.

Silicon wafer-based cells may soon give way to a new generation of thin film photovoltaics. According to The Information Network, a New Tripoli, Pa.,-based market research company for the semiconductor industry, manufacturing methods using cadmium telluride, CdTe, and copper indium gallium selenide, CIGS, will see a tremendous boost in research dollars for future equipment manufacture. A 275% increase in investment by 2010 is expected, which is a testament to their anticipated impact.CIGS and CdTe rely on the deposition of nanoparticles of the precursor materials on the substrate, followed by in-place sintering. The U.S. Dept. of Energy's National Renewable Energy Laboratory, Golden, Colo., says the best CIGS cell now matches the efficiency of the best polycrystalline-silicon cell, about 19.5% efficiency. Potential applications include newspaper-like roll-to-roll printing and CIGS-based inks.

Jump for more...

http://www.rdmag.com/ShowPR.aspx?PUBCODE=014&ACCT=1400000100&ISSUE=0704&RELTYPE=PR&Cat=0&SubCat=0&ProdCode=00000000&PRODLETT=AP&SearchText=thin%20films&CommonCount=0