Organic solar cells usually consist of two layers of semiconductors - one acts as a donor, the other as an acceptor. In contrast to conventional silicon, which is produced using a great deal of energy, the polymer layers can be transferred from a solution directly onto a carrier film. On the one hand, this means comparatively low production costs and, on the other hand, the flexible modules can be used more versatilely in urban areas than silicon cells. For a long time, fullerenes, carbon-based nanoballs, were regarded as ideal acceptors, but the intrinsic losses in fullerene-based composites limit the efficiency potential too much. The FAU has therefore made a paradigm shift: Together with their Chinese partners, the scientists found a new organic molecule that absorbs more light than fullerenes; in addition, it is very durable.