Abstract
Poly(isoindigo-alt-3,4-difluorothiophene) (PIID-[2F]T) analogues used as "polymer acceptors" in bulk-heterojunction (BHJ) solar cells achieve > 7% efficiency when used in conjunction with the polymer donor PBFTAZ (model system; copolymer of benzo[1,2-b: 4,5-b'] dithiophene and 5,6-difluorobenzotriazole). Considering that most efficient polymer-acceptor alternatives to fullerenes (e.g. PC61BM or its C-71 derivative) are based on perylenediimide or naphthalene-diimide motifs thus far, branched alkyl-substituted PIID[2F] T polymers are particularly promising non-fullerene candidates for "all-polymer" BHJ solar cells.