Yao Chen, Hongliang Lei, Seunglok Lee, Peihao Huang, Gengsui Tian, Lei Liu, Tianyu Zeng, Changduk Yang, Tainan Duan, Huanyu Zhou, Zeyun Xiao, Tobin J. Marks, Antonio Facchetti
High Resolution Image Download MS PowerPoint Slide The strategic molecular design of nonfullerene acceptors (NFAs) plays a crucial role in enhancing the efficiency of organic solar cells (OSCs). Here, working from first-principles theoretical computation, we report a new series of quinoxaline-based NFAs ( Qx-PhHal, where Hal = F, Cl, or Br) with varying halogen substitution on the central acceptor core of the molecules to investigate their impact on OSC performance. Notably, OSCs incorporating the brominated NFA demonstrate a significantly higher power conversion efficiency (PCE = 17.58%) than those with fluorinated or chlorinated NFAs (∼14%). Theoretical and experimental analyses reveal that bromination enhances electrostatic interactions, donor–acceptor miscibility, crystallinity, and fibrillar film morphology versus the other halogenated NFAs, thereby enhancing exciton dissociation efficiency, more balanced hole/electron mobility, and reduced exciton recombination rates in the corresponding OSCs. Additionally, ternary solar cells incorporating the brominated NFA as the third component achieve a very high PCE of 20.14%. These findings provide valuable insights into the molecular design of future high-performance NFAs for OSC applications.