Solar Panels

TEM Structure Analysis

The cost of solar electricity has been reduced 100-fold over the past two decades, but further reductions are needed before solar power is widely used. Scientists at the National Renewable Energy Laboratory took major steps toward this goal by designing photovoltaic cells (which convert sunlight to electricity) with 30 percent efficiency, much higher than the 10-20 percent levels achieved previously. The new cells consist of thin layers of semiconductors applied to a low-cost backing, such as glass or plastic. The researchers received Office of Science support to develop a basic understanding of the opto-electronic properties of various semiconductors. Calculations of electronic structure provided the knowledge needed to precisely engineer layered semiconductors. Then, a tandem device was designed with two solar cells made of materials that respond to different parts of the solar spectrum; the top cell (made of gallium indium phosphide) absorbs the high-energy component of sunlight and passes the rest to the bottom cell (made of gallium arsenide) for absorption. Researchers are working on the addition of a third cell to push efficiency to more than 40 percent, to open up new opportunities for terrestrial and space applications.

Scientific Impact: These advances have added to the scientific and engineering knowledge base needed to make solar power more practical and useful. For instance, the material used in the top layer of the new device is much more resistant to radiation damage than conventional silicon and thus will have a longer useful life.

Social Impact: The technology was transferred to a major supplier of photovoltaic cells for space power, and four satellites using it are in orbit, flashing back telephone and television signals. The new solar cells provide as much as 50 percent more power than previous cells, so the satellites can carry more communications links, experiments, or other projects and operate more economically.

Reference: Cotal, H. L.; Lillington, D. R.; Ermer, J. H.; King, R. R.; Karam, N. H.; Kurtz, S. R.; Friedman, D. J.; Olson, J. M.; Ward, S.; Duda, A.; Emery, K. A.; Moriarty, T. (2000). "Highly Efficient 32.3% Monolithic GaInP/GaAs/Ge Triple Junction Concentrator Solar Cells." Program and Proceedings: NCPV Program Review Meeting 2000, 16-19 April 2000, Denver Colorado. BK-520-28064. Golden, CO: National Renewable Energy Laboratory; pp. 111-112; NICH Report No. CP-520-29664.

URL: http://www.nrel.gov/ncpv/pvmenu.cgi?site=ncpv&idx=1&body=world.html

Technical Contact:

Press Contact: Jeff Sherwood, DOE Office of Public Affairs, 202-586-5806

SC-Funding Office: Office of Basic Energy Sciences