Suniva, which began producing monocrystalline silicon cells last October, has raised $75 million.

The Norcross, Ga.-based startup lined up the C round from Warburg Pincus and Apex Venture Partners, as well as previous investors New Enterprise Associates, HIG Ventures and Advanced Equities.

Suniva raised $50 million in February 2008 to build its first factory. It started production on a 32-megawatt line last October, after it announced roughly $1 billion worth of contracts with Solon in Germany and Titan Energy Systems in India last year (see Suniva Scores $480M Solar Cell Contract). Suniva makes cells and sell them to panel makers.

The company has reached the full production rate, said company spokesperson David Briggs. The cells have been assembled into panels, which are available in the U.S. market, Briggs said. Is Solon is using Suniva's cells at its factory in Arizona? Wendy Rosen, another company spokesperson, ducked the question and would only say, "Suniva hasn't announced any specific partners."

Suniva is now gearing up to add a 64-megawatt production line at the same factory in Norcross this summer, Suniva said.

Founded in 2007, Suniva's technology came from the research of Ajeet Rohatgi at the Georgia Institute of Technology's University Center of Excellence for Photovoltaic Research. Rohatgi serves as Suniva's chief technology officer.

The company focuses on improving screen-printing solar cells, a common manufacturing technology, and lowering production costs for monocrystalline silicon cells. Changes that Suniva is implementing enable the cells' semiconductors to produce more power and reduce electron losses.  

Suniva hasn't disclosed its manufacturing costs.

Monocrystalline silicon cells are more challenging and expensive to make than multicrystalline silicon cells, but they are more efficient at converting sunlight into electricity.

Suniva said the solar cells that roll off its factory could convert at least 18 percent of the sunlight that hits the cells into electricity.

San Jose, Calif.-based SunPower currently produces the most efficient monocrystalline silicon solar cells and turns them into panels for the market. The public company is shipping cells with 22.5 efficiency.

China-based Suntech Power, meanwhile, has produced monorystalline cells capable of achieving near 19 percent efficiency, the company said in March this year.

SunPower's former chief operating officer, PM Pai, joined Suniva's board of directors earlier this year.