A solar cell produced by Boeing Spectrolab under a subcontract with the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory is among this year's most significant innovations, as judged by Research & Development (R&D) Magazine.
The NREL/ Boeing Spectrolab R&D 100 Award for 2007 recognizes the High-Efficiency Metamorphic Multi-junction (HEMM) Concentrator Solar Cell, the first solar cell to break the 40 percent conversion efficiency barrier - the solar equivalent of breaking the four-minute mile.
"This R&D 100 award is another important milestone in NREL's 30 year history of developing clean energy technologies, many of which are now available to the consumers," Director Dan Arvizu said. "Breaking the 40 percent barrier is a significant step in reducing the cost of solar energy, a goal set by the President in his Solar America Initiative."
"Once again, DOE's labs are at the cutting edge of innovation with new technology developments to enhance America's economic and national security," U.S. Secretary of Energy Samuel Bodman said. "My heartiest congratulations to the DOE researchers and scientists that have won R&D Magazine's prestigious awards this year."
The Boeing Spectrolab HEMM approach represents a powerful new technology for designing super-efficient multi-junction solar cells. The HEMM solar cell is a triple-junction device - a solar cell with three layers - that uses "mismatched" materials. Typically in a triple-junction cell the atoms are evenly spaced, which generally results in superior electrical performance. But, with the HEMM approach, the atoms are unevenly spaced, giving designers more materials to choose from to create even higher-efficiency solar cells.
"This lattice-mismatched design gives designers a greater freedom in multi-junction cell design for greater absorption and use of sunlight," said Dr. Martha Symko-Davies, research senior supervisor. "This could lead to four, five, and six-junction cells that can convert more than 50 percent of the solar spectrum to electricity."
The HEMM solar cell has a conversion efficiency of 40.7 percent at 240 suns. This means that when sunlight concentrated up to 240 times the normal intensity of the sun is focused onto the cell, 40.7 percent of that solar energy is converted into electrical energy. NREL researchers who worked on this project are Symko-Davies and Dr. Larry Kazmerski, director of the National Center for Photovoltaics at NREL. The results of the cells efficiency were confirmed by NREL's Photovoltaic Cell and Module Performance Characterization section managed by Keith Emery. This brings to 40 the number of R&D 100 Awards earned by the Laboratory.
NREL is the U.S. Department of Energy's primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for DOE by Midwest Research Institute and Battelle. The Laboratory opened its doors on July 5, 1977 as the Solar Energy Research Institute. It was made a national laboratory in 1991.