Naphthobistriazole based non-fused electron acceptors for organic solar cells

Abstract

Near-infrared electron acceptors play an important role in organic solar cells (OSCs), in which they can usually be divided into fused and non-fused electron acceptors. In this work, we reported the first naphthobistriazole (NT) based non-fused electron acceptors for OSCs. The new acceptors contain NT unit as the central core, cyclopentadithiophene as π-bridge and 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC) as end groups. In addition, two or four fluorine (F) atoms were introduced into IC end groups to tune the physical and crystalline properties of the acceptors. The new acceptors were found to exhibit broad absorption spectra in the range of 300–900 nm and deep frontier energy levels when bearing F atoms. OSCs based on these acceptors provided PCEs of 6.19–10.79%, in which F based NT-acceptors showed higher PCEs due to the larger crystallite size, higher exciton dissociation efficiency, higher charge carrier mobilities and hence low charge recombination in solar cells.