An Electron‐Accepting Chromophore Based on Fluorene and Naphthalenediimide Building Blocks for Solution‐Processable Bulk Heterojunction Devices

We have designed, synthesized and utilized a new non‐fullerene electron acceptor, 9,9′‐(9,9‐dioctyl‐9 H ‐fluorene‐2,7‐diyl)bis(2,7‐dioctyl‐4‐(octylamino)benzo[ lmn ][3,8]phenanthroline‐1,3,6,8(2 H ,7 H )‐tetraone) ( B2 ), for use in solution‐processable bulk‐heterojunction devices. B2 is based on a central fluorene moiety, which was capped at both ends with an electron‐accepting naphthalenediimide functionality. B2 exhibited excellent solubility (>30 mg mL −1 in chloroform), high thermal and photochemical stability, and appropriate energy levels for use with the classical polymer donor regioregular poly(3‐hexylthiophene). A power conversion efficiency of 1.16 % was achieved for primitive bulk‐heterojunction devices with a high fill factor of approximately 54 %.