"There will be significant supplies of raw [silicon] material beginning in 2010," said Paula Mints, principal analyst with Navigant Consulting (Palo Alto, Calif.), speaking at a recent IEEE event on solar energy. "This will exert extreme downward pressure on average prices for all technologies, but particularly thin films," she added.

Intermittent shortages of raw silicon have been an issue for both chip and solar panel makers for years. The latest shortage started in 2004 and has mainly affected makers of crystalline silicon solar panels.

Solar panel sales have been rapidly rising in the last several years, but the silicon shortage prevented the panel makers using crystalline technology to fully respond to demand. Thus silicon-based panels declined from about 93 percent to about 89 percent market share from 2004 to 2007, said Mints. The solar industry will become the largest user of raw silicon in 2008, outpacing the semiconductor industry, she said.

Vendors using one of several thin film technologies were able to capitalize on the shortage because they required very little silicon. First Solar Inc. (Tempe, Ariz.) was among the leaders of the group, rising to become the fifth largest panel maker in 2007 with its cadmium telluride-based technology.

But the tide is turning. Supply of silicon is easing this year and could be in overcapacity by mid-2010, Mints forecasts. That should benefit the crystalline vendors who make up nine of the top ten panel makers.

Crystalline vendors have been working hard to minimize their use of silicon. SunPower Corp. (San Jose), ranked as the tenth largest panel maker, slashed its use of silicon per solar cell in half from about 12 to six grams, said SunPower President Richard Swanson.

Rajeeva Lahri, president of Signet Solar Inc. (Menlo Park, Calif.), a thin film company, remains bullish on the technology which he said could expand to serve 40 percent of photovoltaic sales by 2020.

Mark Pinto, chief technology officer of Applied Materials, which supplies Signet's manufacturing equipment, took an even handed view, saying silicon and thin film technologies will serve different sectors of the solar market.

The thin film technologies have plenty of financial backing, spawning as many as two dozen companies in recent years. U.S. companies and venture capitalists spent $350 million on thin film technologies in 2007, said Lawrence Kazmerski, director of the National Center for Photovoltaics at the National Renewable Energy Laboratory.

"That's more than twice what the federal government spent in photovoltaics overall," he said. "You have to worry about so much money going into this [technology]. Not all these companies will survive."