Stepwise Multidimensional Asymmetric Design of Dimeric Acceptors Enables Simultaneous Ordered Packing and High PLQY...

Dimeric molecule acceptors (DMAs) are promising for organic solar cells (OSCs) due to their superior stability and high efficiency. However, further efficiency advancement is critically constrained by a fundamental trade‑off between achieving ordered molecular packing for efficient charge transport and maintaining high photoluminescence quantum yield (PLQY) for suppressed non‑radiative recombination loss (E_nr). In this study, for the first time, we propose a stepwise multidimensional asymmetry engineering to overcome the dilemma and develop three DMAs with progressively increasing asymmetry, namely symmetric C1, mono‑asymmetric C2, and dual‑asymmetric C3. As asymmetric dimension increases, molecular dipole gradually rotates from perpendicular direction for C1 to tilt direction for C2, then to nearly in‑plane for C3, inducing slipped J‑aggregation of C3 with slightly loosened stacking yet enhanced crystal coherence length, which is conducive to efficient charge transport. Meanwhile, among these DMAs, dual‑asymmetric C3 exhibits the most suppressed backbone vibrations due to enhanced molecular rigidity, leading to the highest PLQY and thus the lowest E_{n r}. Consequently, PM6:C3 device achieves a top-level efficiency of 19.87%, outperforming the PM6:C1 (17.88%) and PM6:C2 (18.54%) counterparts. Moreover, D18:L8-BO:C3 device delivers a remarkable PCE of 20.64%. This work demonstrates that multidimensional asymmetric engineering simultaneously enables ordered molecular packing and high PLQY for high‑performance DMAs.