start-up company that is working to develop and produce cheaper solar cells says it will announce today that it has raised $6.5 million from two leading venture capital firms.

The investment is one of the latest signs that alternative energy companies are attracting serious financial interest in high-technology circles,

The money raised by the company, NanoSolar, based in Palo Alto, Calif., is seen as a harbinger because of the strong Silicon Valley pedigree of the venture capital firms — Benchmark Capital and US Venture Partners — and the track record of its chief executive and co-founder, R. Martin Roscheisen. He has already helped start three successful companies. The most recent, eGroups, was sold to Yahoo in 2001 for $720 million.

NanoSolar is one of several companies with promising technologies aimed at narrowing the gap between the cost of solar power and energy from fossil fuels. With conventional information-technology companies in a protracted slump, investors are taking a fresh look at companies working on renewable energy.

Draper Fisher Jurvetson, a venture capital firm in Redwood City, Calif., invested $6.5 million last year in Konarka Technologies, a company in Lowell, Mass., developing low-cost flexible solar panels. And Idealab, a technology incubator in Pasadena, Calif., led by Bill Gross, is behind Energy Innovations, a start-up company working on an engine that could convert sunlight into electricity.

"We think that there's a tectonic shift coming," said Tim Draper, a partner at Draper Fisher. With a finite supply of fossil fuels, over time the price of conventional energy will increase, he said. "That allows some of these alternatives to come in."

Solar power, in particular, is going through a new cycle of innovation as advances in materials science and nanotechnology, which uses materials as small as molecules, are paving the way for approaches that could drastically lower the cost of solar energy.

A new generation of solar cells based on lightweight conductive plastics could cost as little as $40 a square meter, compared with $400 for the silicon panels that have been used since the 1970's. These so-called organic solar cells could make solar a viable option even without government subsidies, experts say.

Unlike silicon, plastic cells do not require high temperatures or equipment similar to that used to manufacture computer chips. They are also more flexible and therefore may be easier to use in a range of places, including rooftops, window blinds, cars, or even clothing.

Plastic cells have their drawbacks, however. They are less efficient than silicon, at least for now, and are not expected to hit the market until 2005.

NanoSolar asserts that it has solved some of the thorniest problems inherent in working with organic materials. The company, applying technology licensed from Sandia National Labs, says it has brought an architectural approach to the process, using self-assembling nano-structures that should substantially improve the energy efficiency of its solar cells.