 The performance of organic solar cells is strongly influenced by the properties of the photovoltaic active layer. In particular, the energetics at the donor, D, acceptor, A, interface determine the properties of charge transfer, CT, states and limit the open circuit voltage. More generally, energetic landscapes in thin films are affected by intermolecular, van der Waals, dipole, and quadrupole interactions which vary with D, a mixing ratio and impact energy levels of free charges, ionization energy, electron affinity, and excitons, singlet, CT states. Disentangling how different intermolecular interactions impact energy levels and support or hinder free charge generation is still a major challenge. In this study, we investigated interface energetics of bulk heterojunctions using sensitive external quantum efficiency measurements and varied the D in mixing ratios of ZNPC or its fluorinated derivatives and C60. As the donor fluorination increased, the energetic offset between FX-ZNPC and C60 decreased. Moving from large to low offset systems, we found qualitative differences in device performance with DC. This article was authored by Anna Jungloth, Pascal Kienberg, Andreas E. Lortzen, and others. We are article.tv, links in the description below.