Climate change and ever scarcer fossil resources will determine the energy mix of the future. Solar energy will play an integral role in this regard. Dr. Andreas Bett and Dr. Frank Dimroth of the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg developed metamorphic triple-junction solar cell consisting of III-V compound semiconductors: gallium indium phosphide, gallium indium arsenide and germanium.

This special structure makes it possible to optimize the use of almost the entire solar spectrum for energy production. Researchers have been able to transform more sunlight into power than ever before, at a record degree of efficiency of 41.1 percent. In recognition of their work, they are receiving the 2010 Joseph von Fraunhofer Prize.

This high degree of efficiency is made possible by stacking multiple top-quality solar cells on top of each other. "Our triple solar cell consists of more than 20 individual layers, all of which we have optimized," says Dr. Frank Dimroth.

"We have improved both the structure of the semiconductor as well as the material quality, the metal contacts and the antireflection coatings, in order to arrive at this result." Originally, these compound solar cells were engineered for use in space - most satellites in space are loaded with them. They supply the operating power. Since the production process is comparatively expensive, these cells had not been used on earth before.

The combination of highly efficient cells with a lens amplifier ensures that - in comparison to conventional solar modules - only one five-hundredth of the semiconductor surface will be needed. The cells within their own specially designed concentrator modules measure only three square millimeters in size.

(Solar Daily)

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