Solar Energy Advances | July 30, 2007 Issue - Vol. 85 Issue 31 | Chemical & Engineering News
Volume 85 Issue 31 | p. 15 | News of The Week
Issue Date: July 30, 2007

Solar Energy Advances

New technology should lead to increased supplies
Department: Science & Technology | Collection: Green Chemistry
New process yields easier route to polysilicon for solar cells.
Credit: Wacker Chemie
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New process yields easier route to polysilicon for solar cells.
Credit: Wacker Chemie

AS THE WORLD increasingly looks to solar power as a new source of energy, technology advances and new cooperation agreements among photovoltaic industry leaders promise to increase the supply, processibility, and cost-efficiency of silicon-based solar energy cells.

Using new technology, Wacker Chemie plans to build a solar-grade granular polysilicon production facility at its site in Burghausen, Germany. The 650-metric-ton-per-year plant should come on-line at the end of 2008 and will manufacture the polysilicon used to make solar wafers in a continuous fluidized-bed process.

The firm first announced two years ago that it had developed the process as an alternative to the batch production procedure now more widely used to make polysilicon for both semiconductors and solar cells. The starting material, trichlorosilane, is the same for both batch and continuous processes.

In the batch process, trichlorosilane is deposited at high temperature on a starter rod, where it decomposes to polysilicon. Workers then remove the rods from the reactor, transfer them to crushing machines that create manageable polysilicon pieces, and run the pieces through an acid-etching step to remove contamination introduced during crushing. The continuous process eliminates the rod removal, crushing, and etching steps.

Taking its advances in solar polysilicon a step further, Wacker also says it is in talks with Schott Solar, a German maker of photovoltaic components, to set up a 50-50 joint venture to make silicon ingots and solar wafers, precursors for the production of solar cells. The two hope to conclude discussions and start up production later this year.

Separately, Germany's Q-Cells, which claims to be the world's second-largest maker of silicon solar cells, has increased its stake in a smaller U.S. silicon cell maker, Solaria, from 12% to 33%. Q-Cells acquired its increased stake in the Silicon Valley-based firm as part of a $50 million investment it made together with two financial investors and Moser Baer, an Indian maker of photovoltaics.

Along with the investment, Q-Cells committed to supplying Solaria with enough cells to generate 1.35 gigawatts of power over the next 10 years. Using its "cell multiplication technology," Solaria will double the output of cells it obtains by slicing them into thin strips and reassembling them to double the surface area they cover. The technology includes packaging the cells under an optical concentrator to focus more sunlight on them.

DuPont is also doing its part to improve solar-cell efficiency. The firm will manage prototype development and testing of a solar cell designed by the University of Delaware that has the potential to be 30% more efficient than existing solar cells. The U.S. Defense Advanced Research Projects Agency awarded a DuPont/University of Delaware consortium $12 million to advance solar-panel development, but it could award as much as $100 million over the three-year life of the project.

 
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