III-V multi-junction solar cells currently hold the record for the highest efficiencies among all photovoltaic technologies. These cells are not only extremely efficient but also robust and long-term stable. However, their widespread adoption has so far been limited due to material and manufacturing costs that are approximately one hundred times higher than those of standard silicon solar cells. Fraunhofer ISE is now working to significantly reduce the production costs of III-V multi-junction cells in the coming years, aiming to make their use economically viable for both concentrator and flat-plate photovoltaic modules. “Thanks to the support of the Werner Siemens Foundation, we are able to pursue further fundamental research and test innovative ideas which advance the scientific foundations of this III-V technology,” says Dr. Frank Dimroth, one of the project leaders. In the coming years, the research will focus on developing reusable substrates for III-V epitaxy, as well as highly cost-effective and scalable epitaxy and manufacturing processes for solar cell production.

In addition, next-generation concentrating photovoltaic (CPV) modules will be developed and demonstrated as part of the project. The Fraunhofer-Gesellschaft is supporting the upcoming research activities with an additional 1.4 million euros. The Werner Siemens Foundation supports outstanding innovations in life sciences, natural sciences, and engineering. With significant funding, it supports excellent researchers with their exceptional research ideas. "Photovoltaics is a key technology to achieve the energy transition – the impact of new techniques that utilize sunlight even more efficiently would be enormous," says Dr. Hubert Keiber, the chairman of the foundation's board. "We are convinced that highly efficient III-V tandem photovoltaics can contribute to this."

Fraunhofer ISE has been developing III-V multi-junction solar cells for more than 20 years. In this type of cell, two to six sub-cells made of III-V compound semiconductors or germanium are stacked on top of each other to optimally utilize sunlight. The institute holds numerous records in this field, particularly for the world's most efficient solar cell with 47% efficiency and the most efficient hybrid concentrator PV module with 350 watts/m² output. Due to their high efficiency, significant amounts of resources and energy can be saved in production. In space, III-V multi-junction solar cells have reliably powered satellites for over 20 years.