 Organic solar cells with low energy offsets have been found to be inefficient due to field-dependent free-charge generation and photo luminescence. This study investigates the origin of these phenomena in non-fullerine acceptors, NFAs, such as Y5, which has a lower energy offset than fullerines. The authors use time-delayed collection field, TDCF, measurements to determine the effect of the electron transport layer and active layer thickness on the performance of the device. They also introduce a new method of TDCF called MTDCF to eliminate any artifacts caused by non-geminate recombination of photo-generated and dark charge carriers near the electrodes. The results suggest that the free-charge generation is controlled by the field-dependent dissociation of local excitons into charged transfer states. Furthermore, the authors find that there is no correlation between the photo-current generated and the steady-state photo-luminescence intensity, suggesting that the photo-current is not related to the luminescence. This article was authored by Manasi Pranav, Thomas Holtzsch, Artem Muzienko, and others. We are article.tv, links in the description below.