Enhancing Performances of Solution‐Processed Inverted Ternary Small‐Molecule Organic Solar Cells: Manipulating the Host‐Guest Donors and Acceptor Interaction

Abstract

The nanoscale morphology of the active layer is critical in determining the power conversion efficiency (PCE) and stability of a bulk hetero‐junction organic solar cell (OSC). In this communication, we present an exciting approach focusing on morphological control to improve the performances of solution‐processed inverted small‐molecule OSCs. A crystalline “guest” electron donor favorably interacting with the “host” donor (via exciplex formation) is introduced to achieve a beneficial morphology, which is solvent additive and post‐solvent vapor annealing free. Specifically DPP(TBFu) 2 that could readily phase separate with the acceptor PC 61 BM under thermal annealing is chosen as the guest donor to enhance the crystallinity and domain purity of the host donor and hence suppress bimolecular recombination. The host‐guest donors exhibit a high miscibility. Upon incorporating 10–20% DPP(TBFu) 2 , the ternary solar cells provided an increase of PCE up to 7.1% with enhanced J sc and fill factor FF , in contrast with 5.5% for the original DPPEZnP‐TEH:PC 61 BM binary cell, while V oc remained almost intact. At 50% loading, the phase separation is over enlarged, leading to performance deterioration. This work shall contribute to developing high‐performance printable small‐molecule OSCs by manipulating the complicated component interactions in the ternary blend.