Monodisperse Low-Bandgap Macromolecule-Based 5,5′-Bibenzo[c][1,2,5]thiadiazole Swivel Cruciform for Organic Solar Cells

Abstract

A novel low bandgap star-like macromolecule was synthesized and applied as electron donor material in the bulk heterojunction solar cells, in which the 5,5′-bibenzo­[c]­[1,2,5]­thiadiazole was used as the central node, in conjunction with four conjugated donor–acceptor arms. Compared with the corresponding small molecule with first generation arms, the macromolecule with second generation branches exhibited significantly enhanced photovoltaic device performances (blended with PC71BM as the active layer) due to dramatically improved short-circuit current density (<i>J</i>_sc) and fill factor (FF). The improvement in <i>J</i>_sc and FF can be attributed to the more broad absorption and the more favorable phase separation when comparing a monodisperse macromolecule with the second generation arms (SFTBT) with a small molecule with first generation branches (DFTBT)