Non-fullerene acceptors with branched side chains and improved molecular packing to exceed 18% efficiency in organic solar cells

作者：Li, Chao; Zhou, Jiadong; Song, Jiali; Xu, Jinqiu; Zhang, Huotian; Zhang, Xuning; Guo, Jing; Zhu, Lei; Wei, Donghui; Han, Guangchao; Min, Jie; Zhang, Yuan; Xie, Zengqi; Yi, Yuanping; Yan, He; Gao, Feng; Liu, Feng^*; Sun, Yanming^*

来源：Nature Energy, 2021, 6(6): 605-613.

DOI：10.1038/s41560-021-00820-x

Molecular design of acceptor and donor molecules has enabled major progress in organic photovoltaics. Li et al. show that branched alkyl chains in non-fullerene acceptors allow favourable morphology in the active layer, enabling a certified device efficiency of 17.9%. @@@ Molecular design of non-fullerene acceptors is of vital importance for high-efficiency organic solar cells. The branched alkyl chain modification is often regarded as a counter-intuitive approach, as it may introduce an undesirable steric hindrance that reduces charge transport in non-fullerene acceptors. Here we show the design and synthesis of a highly efficient non-fullerene acceptor family by substituting the beta position of the thiophene unit on a Y6-based dithienothiophen[3,2-b]-pyrrolobenzothiadiazole core with branched alkyl chains. It was found that such a modification to a different alkyl chain length could completely change the molecular packing behaviour of non-fullerene acceptors, leading to improved structural order and charge transport in thin films. An unprecedented efficiency of 18.32% (certified value of 17.9%) with a fill factor of 81.5% is achieved for single-junction organic solar cells. This work reveals the importance of the branched alkyl chain topology in tuning the molecular packing and blend morphology, which leads to improved organic photovoltaic performance.

• 单位
  北京航空航天大学; 中国科学院; 上海交通大学; 武汉大学; 郑州大学