The Fraunhofer Institute for Solar Energy in Freiburg has developed a PV based on a thin film structure of two semiconductors: gallium indium arsenide and gallium indium phosphide. Solar concentrators are incorporated in the cell which increases the solar intensity by factors ranging from 100 to 1000. Because the optical concentrators focus solar energy onto a small area, this reduces the area of cells required for a given output. In the laboratory the cells achieve an efficiency of 29% but values up to 35% are expected to result from further developments. The disadvantage of this technology is that the concentrators are really only efficient in sunlight.
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