Molecular engineering of non-fullerene small-molecule acceptors (SMAs) plays a key role in enhancing the performance of organic solar cells. An effective strategy is to introduce functional groups into SMA end groups to tune the electronic and morphological properties of polymer/SMA blends. Here, molecular dynamics simulations and long-range corrected density functional theory calculations are combined to examine the impact of the position of methoxy substitution in the SMA end groups. As representative systems, blends of the IT-OM small-molecule acceptor with the PBDB-T polymer donor are explored; three different positions of the methoxy substitution of the IT-OM end groups are examined. By considering intermolecular mixing and packing, the energetic distribution of the charge-transfer electronic states, the exciton-dissociation and non-radiative recombination processes, and the electron-transfer rates among adjacent acceptors, we provide a comprehensive molecular-scale rationalization of the significant experimental variations in device performance for PBDB-T/IT-OM-based solar cells as a function of methoxy position.

非富勒烯小分子受体（SMA）的分子工程学在增强有机太阳能电池的性能中起着关键作用。一种有效的策略是将官能团引入SMA端基，以调节聚合物/ SMA共混物的电子和形态学特性。在这里，分子动力学模拟和远程校正的密度泛函理论计算相结合，以检查SMA端基中甲氧基取代位置的影响。作为代表性的系统，研究了IT-OM小分子受体与PBDB-T聚合物供体的共混物。检查了IT-OM端基的甲氧基取代的三个不同位置。考虑分子间的混合和堆积，电荷转移电子态的高能分布