Quadrupole Solid Additive Engineering-Induced Interactions with Both a Donor and an Acceptor Enable Organic Solar Cells Achieving 19.6% Efficiency

Morphology, which affects the dissociation of excitons and charge transport, determines the performance of organic solar cells (OSCs). Solid additives provide a powerful strategy for improving the molecular packing and fine-tuning the blend morphology. However, current research on additives has primarily focused on those with large dipole moments. Studies on quadrupolar solid additives remain limited, and the potential mechanisms by which the quadrupole moment influences the morphology of the active layer and device performance remain insufficiently understood. Herein, we designed and synthesized the quadrupole solid additive 2,5-di(thiophen-2-yl)pyrazine (M3) to explore its effect on the performance of the OSCs. The M3 molecule exhibits a planar configuration with a net dipole moment of zero while exhibiting a significant quadrupole moment along the π-π stacking direction (Qzz = -108.35 D), which enhances intermolecular interactions. M3 effectively modulates molecular aggregation and packing, influences crystallization behavior, and thereby optimizes the nanoscale morphology and facilitates efficient charge transfer. Consequently, M3-treated PM6:BTP-eC9 devices obtained a power conversion efficiency (PCE) of 19.16%. Impressively, the PM6:BTP-eC9:L8-BO devices processed with M3 achieve an outstanding PCE of 19.62%. This work provides valuable insights into the design of quadrupolar solid additives and elucidates the potential working mechanism for optimizing the morphology and device performance through quadrupolar solid additive engineering.