Polymer Main-Chain Substitution Effects on the Efficiency of Nonfullerene BHJ Solar Cells

Yuliar Firdaus, Luna Pratali Maffei, Federico Cruciani, Michael A. Müller, Shengjian Liu, Sergei Lopatin, Nimer Wehbe, Guy O.Ngongang Ndjawa, Aram Amassian, Frederic Laquai, Pierre M. Beaujuge*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

74 Scopus citations


“Nonfullerene” acceptors are proving effective in bulk heterojunction (BHJ) solar cells when paired with selected polymer donors. However, the principles that guide the selection of adequate polymer donors for high-efficiency BHJ solar cells with nonfullerene acceptors remain a matter of some debate and, while polymer main-chain substitutions may have a direct influence on the donor–acceptor interplay, those effects should be examined and correlated with BHJ device performance patterns. This report examines a set of wide-bandgap polymer donor analogues composed of benzo[1,2-b:4,5-b′]dithiophene (BDT), and thienyl ([2H]T) or 3,4-difluorothiophene ([2F]T) motifs, and their BHJ device performance pattern with the nonfullerene acceptor “ITIC”. Studies show that the fluorine- and ring-substituted derivative PBDT(T)[2F]T largely outperforms its other two polymer donor counterparts, reaching power conversion efficiencies as high as 9.8%. Combining several characterization techniques, the gradual device performance improvements observed on swapping PBDT[2H]T for PBDT[2F]T, and then for PBDT(T)[2F]T, are found to result from (i) notably improved charge generation and collection efficiencies (estimated as ≈60%, 80%, and 90%, respectively), and (ii) reduced geminate recombination (being suppressed from ≈30%, 25% to 10%) and bimolecular recombination (inferred from recombination rate constant comparisons). These examinations will have broader implications for further studies on the optimization of BHJ solar cell efficiencies with polymer donors and a wider range of nonfullerene acceptors.

Original languageEnglish (US)
Article number1700834
JournalAdvanced Energy Materials
Issue number21
StatePublished - Nov 8 2017

Bibliographical note

Funding Information:
Y.F. and L.P.M. contributed equally to this work. This publication is based upon work supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. CRG_R2_13_BEAU_KAUST_1. The authors acknowledge concurrent support under Baseline Research Funding from KAUST. The authors thank KAUST ACL for technical support in the mass spectrometry, GPC, and elemental analyses. The authors thank Z. Kan and M. Babics for the discussions in device characterizations.

Publisher Copyright:
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • 3,4-difluorothiophene
  • ITIC
  • benzo[1,2-b:4,5-b′]dithiophene (BDT)
  • nonfullerene acceptor
  • organic photovoltaics
  • polymer solar cells

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • General Materials Science


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