May 31--SOLAR PANELS churned out at First Solar Inc. in Perrysburg Township have created excitement worldwide because of their low cost and simple design.

Yet seven years after large-scale production started, some experts believe there may be a better way to build this particular mousetrap, modules for converting sunlight into electricity.

The Tempe, Ariz., firm's fast, low-cost production methods continue to encounter intense competition from more established methods and alternative low-cost technologies.

First Solar is among a group of companies using so-called thin-film methods. Some researchers believe that eventually these firms will dominate the industry because their panels, or solar modules, rely on a thin coating of chemicals applied to glass or other surfaces. Because they require less raw material, they are cheaper to produce than traditional panels, which rely on sometimes expensive man-made polysilicon.

The disagreements don't end there. Advocates of thin-film technology differ about which chemical coatings will yield the most efficient panels suitable for mass production.

Even in metro Toledo, which one network news report described as a budding "solar valley" because of pioneering research and manufacturing in thin-film technologies, experts disagree about the best way to trim manufacturing costs while helping reduce the world's addiction to pollution-producing fossil fuels.

Besides First Solar, three other Toledo-linked firms are seeking to commercialize the lower-cost manufacturing methods. Two use thin-film processes similar to First Solar's.

The third, Xunlight Corp., is banking on a different thin-film process that replaces the glass used by the others with a thin layer of stainless steel and a different combination of chemical compounds.

Xunlight, now in pilot production of solar panels that can be rolled up for shipping, doesn't expect to begin making products for sale until late 2009 or early next year. "I expect our cost to be similar to First Solar when we get to similar capacity," said Chief Executive Xunming Deng.

He refrained from criticizing First Solar or its approach to manufacturing. "First Solar is a very well-run company," Mr. Deng said in a telephone interview from Munich, where he was promoting Xunlight panels at a trade fair. "They have been serving as a role model in the ... industry."

The issue of who has the best technology takes on increased importance now, because many panel producers are struggling in a supply glut and international credit crisis that has prompted customers to cancel orders and delay construction of solar farms.

"Globally, there's been a kind of softening of demand," said Monique Hanis, spokesman for the Solar Energy Industries Association in Washington. In addition to other developments, some European nations have studied reductions in subsidies for solar power.

First Solar, the world's largest producer of panels using thin-film technology, is among a small number of suppliers that continue to thrive.