Bay Position Substituted Perylene Diimide Derivatives as Cathode Interface Materials for High-Efficient Nonfullerene and Fullerene Organic Photovoltaics

Organic photovoltaics (OPVs) have earned widespread and strong interest on account of their low cost, lightweight, flexibility, solution-processability, and so forth. However, the lack of efficient and universal cathode interface materials (CIMs) limits the further development of OPVs. In this paper, we design and synthesize three bay-position-substituted perylene diimide derivatives (bay-PDIs), which are applied to OPV as CIM for the first time. Three bay-PDIs possess good solubility, suitable energy levels, and good film-forming properties. The introduction of bayPDIs can facilitate desirable cascade energy level alignment, extract electrons from the donor, and smooth the surface of the active layer, thus promoting exciton dissociation, improving charge transport, and suppressing charge recombination. As a result, the OPV device using PDI21 as CIM and PM6:Y6 combination as an active layer achieves an improved power conversion efficiency (PCE) of 16.72% compared with that of the control device (16.08%) with PDINO as CIM, together with enhanced device stability. In addition, the PDI21 interface layer also exhibits excellent performance for other nonfullerenes and fullerene OPVs. Our findings afford a novel approach to developing efficient and universal CIMs for high-efficiency and stable OPVs.