Precise heterodimerization of acceptors for high-efficiency binary organic solar cells

Although dimeric acceptors have demonstrated promising efficacy for improving operational stability of organic solar cells (OSCs), the power conversion efficiencies (PCEs) of corresponding binary devices remain constrained due to their weak intermolecular interactions and undesirable molecular packing. Here, we integrate a dimerization with asymmetric terminal strategy to design a heterodimer acceptor, NVB. Breaking molecular symmetry enhances dipole interactions and optimizes molecular packing, leading to superior charge transport and suppressed recombination. As a result, the PM6:NVB-based device achieves a record-high efficiency of 19.90% (certified as 19.35%), representing the highest value reported for all dimer-based binary devices thus far. Remarkably, the NVB-based device exhibits enhanced stability with a T₈₀ (lifetime for maintaining 80% of its initial efficiency) over 1,500 h, attributed to elevated glass transition temperature (T_g). Overall, this work establishes an “asymmetric dimerization” paradigm that concurrently improves efficiency and stability through molecular engineering, providing a practical pathway toward high-performance OSCs.