Technical Insight
Spectrolab GaAs cells take solar car to race victory (Opto News)
GaAs solar cells from Spectrolab powered the University of Michigan s solar car to its recent victory in the American Solar Challenge. Designed by the Michigan students, the M-Pulse vehicle used a total of 3000 Spectrolab dual-junction terrestrial solar cells in the race. The team took just nine days to complete the course, which began in Chicago and ended 2248 miles away in California. The winning time was slightly over 56 hours (see ). The solar panels generated enough power to charge the batteries even when the car was running at 55 mph. Under normal weather conditions, the cells electrical output was about 1200 W, although they could generate up to 1600 W as a result of solar energy reflected back from clouds. Headquartered in Sylmar, California, Spectrolab is the largest manufacturer of solar cells for space applications. Spectrolab s dual-junction cells comprise GaInP2 and GaAs regions epitaxially grown in series on Ge substrates. Each junction converts energy from a different portion of the solar spectrum, which increases the efficiency compared with a single junction. The cell is designed to be 23.7% efficient in terrestrial applications. The company also provides triple-junction solar cells that have an efficiency of 29%. Cell manufacturers such as Spectrolab and Tecstar are currently working on solar cells with an increased efficiency of 40% (see Compound Semiconductor August 2001, p29).
