An H ‐Aggregation Mediator Enhances Photoluminescence Quantum Yield and Crystallinity for Efficient Nonannealed Organic Solar Cells
Hanjian Lai, Huanyan Jiang, Xingjie Mi, Rujin Zhou, Jun Zhang, Zhenghui Luo, Chao Li, Haoran Hu, Yufei Wang, Yuang Fu, Guoli Wang, Xianyong Zhou, Sha Liu, Xinhui Lu, Guangye Zhang, He Yan, Yanming Sun, Zhenye Li, Chang LiuABSTRACT
Organic solar cells (OSCs) hold promise for building‐integrated and wearable photovoltaics, yet excessive H ‐aggregation of non‐fullerene acceptors (NFAs) quenches luminescence and lowers the photoluminescence quantum yield (PLQY), limiting further efficiency gains. Here, we introduce NTCl‐4F, a molecular H ‐aggregation mediator, into the D18:L8‐BO‐C 4 binary system. Designed with an identical backbone to L8‐BO‐C 4 but featuring a rotatable central core that induces steric hindrance (dihedral angle of 4.87° as revealed by single‐crystal diffraction), NTCl‐4F effectively suppresses H ‐aggregation while promoting ordered J ‐aggregation (with average fibril diameters from 20.75 to 17.16 nm). This aggregation‐mode modulation enhances the PLQY from 6.13% to 7.52%. Furthermore, the ordered J ‐aggregation induced by NTCl‐4F enhances the crystallinity of the system with increased crystal coherence lengths (CCL) and decreased fractal dimension ( D f ), achieving synchronous improvement of short‐circuit current. Consequently, the NTCl‐4F‐modified device achieves a power conversion efficiency (PCE) of 20.8% under non‐annealed conditions, which stands among the highest reported efficiencies for non‐annealed OSCs. The strategy proves general, yielding efficiency improvements in PM6:Y6 and D18:Y7 systems. This work establishes aggregation‐mode engineering via an H ‐aggregation mediator as a versatile route to enhance PLQY and crystallinity for high‐performance OSCs.