Solar Cell Development

Solar cell development has been a key research topic at Fraunhofer ISE since its founding forty years ago with the aim of increasing efficiencies, reducing costs and saving valuable material resources. Our competence in the tandem technology is based on decades of research on the development of multi-junction solar cells. In the concentrator technology we have achieved efficiences up to 47.6 %. This is presently the highest efficiency reached to date by any solar cell worldwide. Largely promising are the newest approaches of tandem cell architectures where we focus on the development of both III-V-silicon and perovskite-silicon tandem solar cells. 

Solar cells with one absorber material can only convert a limited wavelength range of sunlight into electricity optimally while the other wavelengths of the sun’s spectrum are used poorly or not at all. By combining solar cells with different bandgaps, the sun’s spectrum can be used much more efficiently.

Designing a high-efficiency tandem solar cell requires photovoltaic absorber materials with different band gaps. As a rule, the solar cells at the top of the monolithic stack have a large bandgap and convert UV and blue light into electricity, while the solar cells at the bottom of the stack have smaller bandgaps and convert the red and IR light efficiently into electricity.

Our tandem expertise is rooted in our long-standing research on concentrator tandem solar cells based on III-V semiconductors. For unconcentrated applications we are focusing on III-V on silicon and perovskite on silicon structures. For all three material groups – III-V, perovskites and silicon – we have world-class technological facilities and excellent scientific expertise making Fraunhofer ISE to one of the leading research institutes in the development of tandem solar cells.