During the last years he has conducted fundamental and applied research in the field of Organic Semiconductors and Photovoltaics. His expertise covers fundamental structure-property-relations with respect to solution processed organic semiconductors, upscaling of polymer solar cells to modules, modelling of solar cells and modules in device simulations as well as their investigation concerning degradation phenomena and their constructive stabilization for improved operational lifetimes. Another major focus is on the application of imaging-based advanced qualitative and quantitative characterization of photovoltaic devices, thus fostering efforts for commercialization of Organic Solar Cells. He has supervised ~15 undergraduate, and about 10 PhD-students. Harald Hoppe has published over 100 peer reviewed papers and more than 5 book chapters.