Evergreen Solar Pushes the Micron Barrier

String ribbon doesn’t seem to adequately describe a silicon wafer that is less than 150 microns thick, that’s approximately the thickness of three human hairs. But Evergreen Solar has managed to improve their string ribbon technology for silicon wafers, and the company now has the potential to produce their product with a thickness of less than 150 microns.

“Evergreen Solar’s mission since its inception has been to produce high-quality solar products at a fraction of the cost of conventional methods,” said Richard M. Feldt, President and Chief Executive Officer. “With the latest enhancement to our Gemini II double ribbon growth process, (the company) has demonstrated in its pilot operations that it can manufacture wafers using one third of the silicon required by conventional methods.” The enhancements Feldt was talking about are altered growing conditions in the Gemini II furnaces that allow the company to produce silicon wafers that are half the thickness of their current standard. Many wafer manufacturers saw slices off of silicon ingots to produce wafers, according to Brown F. Williams, who is the vice president of Research and Development at Evergreen. Silicon is lost to the saw cut, he said, and the string ribbon process used at Evergreen avoids that loss. “There is some concern that the tightening silicon supplies may limit the growth of the photovoltaic industry for the next year or two, Feldt said. “We expect that production of our thin wafers will entail other savings in material costs, and the thin wafers will perform at a higher level of efficiency.” Evergreen has produced enough of the string ribbon wafers to assemble them into a panel. Now they will work on perfecting their production process, and Feldt said the company expects to achieve production status by the end of 2005.

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