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-9H-fluorene-2,7-diyl)bis(2,7-dioctyl-4-(octylamino)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-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 (>30mgmL-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%.