In order to increase the power conversion efficiency of organic solar cells, their absorption spectrum should be broadened while maintaining efficient exciton harvesting. This requires the use of multiple complementary absorbers, usually incorporated in tandem cells or in cascaded exciton-dissociating heterojunctions. Here we present a simple three-layer architecture comprising two non-fullerene acceptors and a donor, in which an energy-relay cascade enables an efficient two-step exciton dissociation process. Excitons generated in the remote wide-bandgap acceptor are transferred by long-range Förster energy transfer to the smaller-bandgap acceptor, and subsequently dissociate at the donor interface. The photocurrent originates from all three complementary absorbing materials, resulting in a quantum efficiency above 75% between 400 and 720 nm. With an open-circuit voltage close to 1 V, this leads to a remarkable power conversion efficiency of 8.4%. These results confirm that multilayer cascade structures are a promising alternative to conventional donor-fullerene organic solar cells.

The electronic structure at organic/organic interfaces plays a key role, among others, in defining the quantum efficiency of organics-based photovoltaic cells. Here, we perform quantum-chemical and microelectrostatic calculations on molecular aggregates of various sizes and shapes to characterize the interfacial dipole moment at pentacene/C 60 heterojunctions. The results show that the interfacial dipole mostly originates in polarization effects due to the asymmetry in the multipolar expansion of the electronic density distribution between the interacting molecules, rather than in a charge transfer from donor to acceptor. The local dipole is found to fluctuate in sign and magnitude over the interface and appears as a sensitive probe of the relative arrangements of the pentacene and C 60 molecules (and of the resulting local electrical fields sensed by the molecular units).

The complex refractive index of fluorinated subphthalocyanines (SubPcs) deposited by vacuum sublimation is determined by spectral ellipsometry. Their performance as acceptor material is characterized in a range of donor/acceptor heterojunctions in organic photovoltaic cells (OPVCs) by current–voltage measurements under 1 sun AM 1.5D simulated solar illumination and spectral response. Both electron and hole transfer between donor and acceptor materials is demonstrated. Power conversion efficiencies of 0.96% are found with an open‐circuit bias of 940 mV. Hence, it is shown that fluorinated SubPcs can be considered as an acceptor material in OPVCs with an absorption in the visible comparable to that of well‐known metallophthalocyanines.