Not only the most recent discoveries find their way through the cloud of news inventions. Such example is the ultra-efficient metamorphic triple-junction solar cell made by Dr. Andreas Bett and Dr. Frank Dimroth from the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg.
They used Fresnel lenses situated 10 cm apart from stacked layers of solar cells. The metamorphic triple-junction solar cells consist of gallium indium phosphide, gallium indium arsenide and germanium semiconductors. The efficiency of these cells is dazzling: 41.1 percent – higher than ever before. The two scientists even for the 2010 Joseph von Fraunhofer Prize.
“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.”
Until now, these types of solar cells had only been used in satellites, where price didn’t matter much. Combining them with solar concentrators, though, ensures low prices and allows them to be used in land energy harvesting. For that matter, only 1/500 of the semiconductor combination will be used in the actual solar cell, because the Fresnel lenses will amplify the light by a factor of 400 to 500.
Of course, the solar cells would overheat and eventually burn if they didn’t think of a method to cool them. A copper support is connected to each cell, providing passive cooling. “Thanks to this construction, we were able to produce modules with a degree of efficiency in excess of 29 percent,” says Dr. Andreas Bett. These modules have been on the market since 2007 under the brand name FLATCON®, and are being used in a solar park in Spain, for example.
To prove their technology’s viability in terms of manufacturing possibilities, the team set up a demonstrative lab at Fraunhofer, equipped with the same machines used in real factories. By working with Concentrix Solar GmbH, who produces the concentrator systems, and AZUR Space Solar Power in Heilbronn, producing the solar cells, the field is almost set to go and only waits for a more efficient assembly line to be improvised. 2011 is the year AZUR estimates that these efficient solar cells would reach the market.