Concentrated Solar Startup Sets a New Efficiency Record

Technology Review
Feb 3, 2012

Solar tracker: This array of solar modules was built by Semprius for testing. The modules are mounted on a two-axis tracker that keeps them aimed at the sun.
Credit: Semprius

Semprius, a startup that makes miniscule solar cells capable of capturing concentrated sunlight without costly cooling systems, announced this week that it had made the world's most efficient solar panel.

The company's solar panels use tiny solar cells made of gallium arsenide—the record-breaking solar module contains hundreds of such solar cells, each about the width of a line drawn by a ball-point pen, arranged under lenses that concentrate sunlight 1,100 times.

Gallium arsenide is far better at absorbing sunlight than silicon, the material used in most solar cells, but it's also more expensive. Furthermore, although concentrated solar modules use less semiconducting material, they usually require expensive optics, cooling systems, and tracking systems to keep them aimed at the sun. Semprius's microscaled solar cells are inherently much better at dissipating heat, making them cheaper.

Semprius's modules have another advantage: whereas a silicon solar cell only efficiently absorbs a narrow band of sunlight, the solar cells in this module are made of three layers of gallium arsenide, each modified to convert a different part of the solar spectrum into electricity.

Tests by a third-party certified the efficiency of Semprius's solar panel at 33.9 percent, marking the first time any solar module has been able to convert more than one-third of the sunlight that falls on it into electricity. Conventional silicon solar panels typically convert less than 15 percent of light into electricity, and the record for a silicon solar panel is 22.9 percent. The previous record for any solar panel was 32 percent, Semprius says.

One-off, experimental modules have achieved higher efficiencies, but Semprius's record-setting module is designed for commercial use. It was made with the same type of equipment that the company is installing in a small factory in Henderson, North Carolina, that it will open this summer. "It's a good indication of the efficiencies our customers can expect," says Joe Carr, Semprius's CEO.
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Additional Information:

• Semprius Press Release: Semprius Sets World Record for Solar Module Efficiency