Altering alkyl-chains branching positions for boosting the performance of small-molecule acceptors for highly efficient nonfullerene organic solar cells

• 来源期刊: 中国科学:化学（英文版）
• 年，卷（期）: 2020,（3）
• 页码范围: 361-369
• 页数: 9页
• 语种: 英文

摘要

The emergence of the latest generation of small-molecule acceptor (SMA) materials,with Y6 as a typical example,accounts for the surge in device performance for organic solar cells (OSCs).This study proposes two new acceptors named Y6-C2 and Y6-C3,from judicious alteration of alkyl-chains branching positions away from the Y6 backbone.Compared to the Y6,the Y6-C2 exhibits similar optical and electrochemical properties,but better molecular packing and enhanced crystallinity.In contrast,the Y6-C3 shows a significant blue-shift absorption in the solid state relative to the Y6 and Y6-C2.The as-cast PM6:Y6-C2-based OSC yields a higher power conversion efficiency (PCE) of 15.89％ than those based on the Y6 (15.24％) and Y6-C3 (13.76％),representing the highest known value for as-cast nonfullerene OSCs.Prominently,the Y6-C2 displays a good compatibility with the PC71BM.Therefore,a ternary OSC device based on PM6:Y6-C2:PC71BM (1.0:1.0:0.2) was produced,and it exhibits an outstanding PCE of 17.06％ and an impressive fill factor (FF) of 0.772.Our results improve understanding of the structure-property relationship for state-of-the-art SMAs and demonstrate that modulating the structure of SMAs via fine-tuning of alkyl-chains branching positions is an effective method to enhance their performance.