Much progress has been made researching organic solar cells (OSC) in the last two decades, but the field still holds surprises. Until recently, the general assumption was that for efficient operation a mixture of about equal parts of donor and acceptor molecules is required in the photovoltaic active layer of OSC. However, C. Tang, one of the pioneers of OSC, and his team published an OSC with only very little donor molecules (hence the name "homoeopathic solar cells") that should not work at all, or at least not as well as they do according to current understanding. It is not clear to what extend a new operating principle for OSC has been found and literature contains contradicting results. Key objective of this proposal is to use neutrons for the investigating of the so far unknown distribution of donor and acceptor molecules, which holds the key to better understand these solar cells.