A Rockville solar-energy company says it has found a way to increase the output of solar-powered photovoltaic cells by 80 percent over current cell designs.

Solarex Inc., which is the world's largest manufacturer of solar cells, said its Semix materials subsidiary had developed a new way to process silicon crystals, the raw material for the company's solar cells, that will enable the company to make cells within five years that will produce electricity for about 10 cents per kilowatt-hour. Conventionally produced electricity costs between 6.6 cents and 15 cents per kilowatt hour across the nation, the company said.

The divergence in price between conventional and solar electricity has long held back the solar-power industry, experts say, although the gap has been narrowing.

"The implications of this breakthrough are profound," Solarex Chairman Joseph Lindmayer said in making the announcement. "It is the first step in making the wide-scale use of solar energy a not-so-distant reality to homeowners, business, industry and agriculture."

Solarex did not say exactly what the breakthrough was, but said it had to do with the way Semix processes silicon. Semix casts molten silicon into pricks that are then cut wafer-thin, polished, and made into solar cells by Solarex. Some of Solarex's manufacturing is done in a unique "solar breeder" plant in Frederick--a solar-powered factory that makes solar cells.

The company said the breakthrough allows it to convert 17 or 18 percent of the sun's energy into electricity under laboratory conditions, bettering its current rate of 10 to 12 percent for cells actually in commercial use. It says competing technologies, such as a process that makes cells out of thin silicon film, converts only about 10 percent of the sun's energy under laboratory conditions.

Solarex, founded by Lindmayer and another former Comsat scientist a decade ago, has annual revenues of about $20 million and commands about a 40 percent share of the market for solar cells. The privately held company's stockholders include Standard Oil Co. of Indiana, which has about a 30 percent stake.