U.S. Department of Energy

    Solar Power Companies Reach New Heights in Efficiency

    March 3, 2004

    The solar power industry produces a wide variety of products, but every manufacturer tends to focus on two important metrics: the cost of the devices and their efficiency at converting sunlight into electricity. Several companies have recently claimed to break barriers in the latter measurement, commonly referred to as conversion efficiency. Most recently, SunPower Corporation announced that its A-300 crystalline silicon solar cell has achieved an efficiency of 21.5 percent—that is, it converts 21.5 percent of the sunlight hitting it into electricity. According to SunPower, that's a world record for five-inch silicon solar cells, which typically achieve efficiencies of 12 to 15 percent. DOE's National Renewable Energy Laboratory confirmed the cell's efficiency. Back in May 2003, the A-300 made news with a conversion efficiency of 20.4 percent. See the SunPower press release.

    Compared to crystalline silicon solar cells, thin-film solar cells cost less per square foot but also achieve lower conversion efficiencies. For instance, Global Solar Energy, a manufacturer of thin-film solar modules, produced a solar module in early February that achieves a conversion efficiency of 10.7 percent, which the company claims is a record for a flexible thin-film module built on a production line. Meanwhile, Konarka Technologies, Inc. has produced a flexible thin-film solar cell with a conversion efficiency greater than 7 percent, and the company expects to achieve 10-percent efficiencies in the coming months. The company is still in the startup phase and plans to begin pilot-scale production later this year. See the press releases from Global Solar and Konarka.

    While higher conversion efficiencies improve the usefulness of solar power devices, higher-efficiency production processes help to cut costs. Evergreen Solar, Inc. produces crystalline silicon solar cells from ribbons of silicon extracted from molten silicon in a furnace. After showing it could double its production by producing two ribbons of silicon from one furnace about a year ago, the company announced in late January that it had successfully produced four silicon ribbons from one furnace. The company uses a proprietary technique to create the silicon ribbons. See the Evergreen Solar press release.