F-Substituted oligothiophenes serve as nonfullerene acceptors in polymer solar cells with open-circuit voltages >1 V
T. Duan, M. Babics, A. Seitkhan, Y. Firdaus, R.-Z. Liang, F. Cruciani, S. Liu, S. Lopatin, P.M. Beaujuge
Journal of Materials Chemistry A, 6, pp. 9368-9372, (2018)
F-Substituted oligothiophenes, Open-circuit voltages, Nonfullerene, Solar cells
We report on a set of two analogous, F-substituted oligothiophene derivatives (D5T6F-M and D7T8F-M), in which systematic fluorination at the thienyl moieties is shown to induce a sufficient increase in electron affinity (EA; i.e. suppressed LUMO level) and in ionization potential (IP; i.e. deeper HOMO) to (i) impart the molecules with electron-accepting and -transporting characteristics, and (ii) yield high open-circuit voltages >1 V in BHJ solar cells when combined with a low-bandgap polymer donor (PCE10) commonly used with fullerenes. The nonfullerene BHJ devices with the SM acceptor D5T6F-M achieve power conversion efficiencies (PCEs) of up to ca. 4.5% (vs. ca. 2% for D7T8F-M-based devices). Our study shows that –F substitutions in SM systems – otherwise used as donors – is an effective approach in the design of nonfullerene acceptors for efficient BHJ solar cells with polymer donors.
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