Scientists working on "MehrSi", the joint project spearheaded by the Fraunhofer Institute for Solar Energy Systems ISE, have recently achieved unprecedented efficiency levels for specialized solar cells, converting 24.3 percent of the sunlight absorbed by monolithic III-V triple-junction cells grown on silicon into electrical or chemical energy. According to these researchers, this marks a major milestone in the development of new solar cells, with the ultimate aim of replacing conventional silicon solar cells in the future. Another key advantage of these new cells is that they can be used for direct solar water splitting, and thus for producing hydrogen - which is why more than a few experts are currently calling this the renewable energy source of the future. In addition to Ilmenau University of Technology (TU Ilmenau), Fraunhofer ISE also recruited Philipps-Universität Marburg and the system manufacturer Aixtron SE as project partners.

The project, which is funded by the German Federal Ministry of Education and Research, was sparked by a question: What is the best way to combine silicon, the cost-effective material most commonly used in solar cell production, with the powerful III-V semiconductors so that sunlight can be converted into usable energy with maximum efficiency? To find the answer, researchers specializing in the "fundamentals of energy materials" from TU Ilmenau have developed approaches to improve the way the interface between the silicon and the "III-V materials" is prepared. These contact surfaces on solar cells, consisting of two or more layered cells made of different materials, determine the cells' level of performance. For the best possible results, it's important to ensure the atoms are arranged in exactly the right positions in the crystal lattice when growing the III-V layer on silicon, otherwise the properties of the cells can be severely impaired. The improvements made by TU Ilmenau's scientists as part of the "MehrSi" project have reportedly opened the door to manufacturing processes that allow for a virtually flawless transition between the materials.

Technische Universität Ilmenau (98693 Ilmenau, Germany)
www.tu-ilmenau.de