cm6b00131_si_001.pdf (7.48 MB)
π‑Bridge-Independent 2‑(Benzo[c][1,2,5]thiadiazol-4-ylmethylene)malononitrile-Substituted Nonfullerene Acceptors for Efficient Bulk Heterojunction Solar Cells
journal contribution
posted on 2016-02-25, 00:00 authored by Kai Wang, Yuliar Firdaus, Maxime Babics, Federico Cruciani, Qasim Saleem, Abdulrahman El Labban, Maha A. Alamoudi, Tomasz Marszalek, Wojciech Pisula, Frederic Laquai, Pierre M. BeaujugeMolecular acceptors are promising
alternatives to fullerenes (e.g.,
PC61/71BM) in the fabrication of high-efficiency
bulk-heterojunction (BHJ) solar cells. While solution-processed polymer–fullerene
BHJ devices have recently met the 10% efficiency threshold, molecular
acceptors have yet to prove comparably efficient with polymer donors.
At this point in time, it is important to forge a better understanding
of the design parameters that directly impact small-molecule (SM)
acceptor performance in BHJ solar cells. In this report, we show that
2-(benzo[c][1,2,5]thiadiazol-4-ylmethylene)malononitrile
(BM)-terminated SM acceptors can achieve efficiencies as high as 5.3%
in BHJ solar cells with the polymer donor PCE10. Through systematic
device optimization and characterization studies, we find that the
nonfullerene analogues (FBM, CBM, and CDTBM) all perform comparably
well, independent of the molecular structure and electronics of the
π-bridge that links the two electron-deficient BM end groups.
With estimated electron affinities within range of those of common
fullerenes (4.0–4.3 eV), and a wider range of ionization potentials
(6.2–5.6 eV), the SM acceptors absorb in the visible spectrum
and effectively contribute to the BHJ device photocurrent. BM-substituted
SM acceptors are promising alternatives to fullerenes in solution-processed
BHJ solar cells.