"Organic photovoltaics (OPV) are emerging as a potential cheap route to convert solar energy into electricity due to recent progress in the field. The global energy need makes OPV a highly strategically relevant renewable energy approach for European research and industry as very low production costs are envisaged. However, higher power conversion efficiency is paramount for making these devices attractive for the market and a much better understanding of the current principal limitations is needed. The approach of this project is to identifying the dominant electrical limitations for OPVs, and currently disregards the more well-known optical limitations.We aim to accurately determine internal quantum efficiency as a function of both intensity and wavelength of the incident light and the applied voltage for a variety differently performing OPV cells based on selected materials and conditions. We will focus our investigation on the dominant recombination processes, the origin of their voltage and light intensity dependence and their relation to charge transfer states as link between geminate and non-geminate recombination. We aim to disentangle these recombination rates, to be able to better identify the dominant loss routes of charge carriers and to describe their impact on solar cell performance by reconstructing the experimental current-voltage characteristics. We also want to determine the properties affecting radiative and non radiative contributions to recombination by probing radiative quantum yield of charge transfer states and trap assisted recombination.By combining a new set of complementary electro-optical transient experiments, we aim to establish a detailed picture of the loss mechanisms for OPVs between active layer photon absorption and electrons flowing into the external circuit. The results of this project allow providing detailed feedback to both material synthesis and device manufacturing in view of optimizing the performance of OPVs."