8 December 2011

Fraunhofer and CEA-LETI researchers receive Franco-German Business Award

On 5 December in Paris, a team of researchers from the Fraunhofer Institute or Solar Energy Systems ISE in Freiburg, Germany and the Carnot-Institut Laboratoire d‘électronique des technologies de l‘information (CEA-LETI) in Grenoble, France were honored for their international research in developing reusable substrates for III-V multi-junction solar cells by being presented with the Franco-German Business Award 2011 by the Franco-German Chamber of Commerce and Industry AHK.

The award is presented in recognition of best practices over the past two years. Patrons of the award are the French Minister of Economy, Finance and Industry François Baroin and the German Federal Minister for Economics and Technology Dr Philipp Rösler.

Multi-junction solar cells are particularly efficient as they can achieve efficiencies of up to 43% (twice that of conventional solar cells made of crystalline silicon). The technology is used in concentrator photovoltaics (CPV), where lenses focus the light of the sun 500 times onto small solar cells. Concentrator systems produce solar electricity on a large scale, particularly in power plants in areas rich in sunlight. Among the producers of such CPV systems is Freiburg-based SOITEC Solar GmbH, which was spun off from the Fraunhofer ISE in 2005 as Concentrix Solar GmbH before being acquired in December 2009 by SOITEC of Bernin, France, which manufactures engineered substrates including silicon-on-insulator (SOI) wafers (as well as III-V epiwafers through its Picogiga International division).

The multi-junction solar cells consist of about 30 semiconductor layers built up layer by layer on germanium or gallium arsenide substrates. However, these materials are very costly. So, in a joint Franco-German project, researchers at ISE and CEA-LETI are developing new, reusable substrates for multi-junction solar cells. Until now the solar cells had to remain in place atop the germanium or GaAs crystals, but now they are removable from the new substrate, which can be recycled several times. This can reduce the cost of producing solar cells by up to 20%, it is reckoned.

“In the Solar-Bond project, two high-tech institutes have combined their skills,” says Dr Frank Dimroth, head of Department III-V - Epitaxy and Solar Cells at Fraunhofer ISE. “CEA-LETI is a leader in the microelectronics field and Fraunhofer ISE in photovoltaics,” he adds. CEA-LETI develops the substrate and adapts its properties to the requirements of growing multi-junction solar cells; Fraunhofer ISE then applies the solar cells to these substrates and processes them to create ready-to-use devices. The researchers are also working closely with SOITEC: in future, the new solar cells will be used in their concentrator modules.

Solar-Bond is one of 26 projects sponsored under the Programme Inter Carnot Fraunhofer (PICF), which is jointly run by Germany’s Federal Ministry for Education and Research (BMBF) and France’s National Research Agency (Agence Nationale de la Recherche, ANR) for collaborative research and innovation projects between Fraunhofer Institutes (FhI) and Carnot Institutes (IC). The PICF aims to establish strategic partnerships between French and German research and industrial organizations.

Tags: Fraunhofer Institute III-V multi-junction solar cells

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