Nan Wei, Tong Sun, Hao Lu, Xiaodong Wang, Xueqing Ma, Jiahe Zhang, Bohan Shang, Jieni Chen, Wenkai Zhang, Ming Fan, Yukun Xia, Zaifei Ma, Xiangwei Zhu, Zhishan Bo, Yahui Liu
Non-radiative energy loss remains a challenge in organic solar cells. Here we show that introducing bulky chlorobenzene moieties at the end of inner side chains yields two acceptor materials, Y6-2Cl and Y6-4Cl. The introduction of chlorobenzene groups enhances the solubility, while also boosting the photoluminescence quantum yield and inducing a distinct molecular packing mode in Y6-2Cl and Y6-4Cl. Rather than following the conventional three-dimensional network structure observed in Y-series acceptors, these materials form a highly ordered, array-like arrangement while maintaining excellent crystalline characteristics. This unique structural feature not only preserves high charge-transport properties but also optimizes aggregation behavior and morphology of the active layers. The D18:Y6-2Cl binary device demonstrates a PCE of 20.0%. The ternary device composed of D18:L8-BO:Y6-2Cl achieves a PCE of 20.92%, accompanied by a fill factor of 82.93%. Overall, the side-chain functionalization strategy proposed in this study offers a direction for developing high-performance non-fullerene acceptors.