Improved photovoltaic performance of a nonfullerene acceptor based on a benzo[b]thiophene fused end group with extended π-conjugation

Kun Yang, Qiaogan Liao, Chang Woo Koh, Jianhua Chen, Mengyao Su, Xin Zhou, Yumin Tang, Yang Wang, Youming Zhang, Han Young Woo, Xugang Guo

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7 Citations (Scopus)

Abstract

A new indacenodithiophene-based acceptor-donor-acceptor (A-D-A) type nonfullerene acceptor material ITBTC, featuring a conjugation-extended benzo[b]thiophene-fused end group, was designed and synthesized. Compared to the well known phenyl-fused ITIC acceptor containing a 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC) end group, incorporation of an additional electron-rich thiophene into the IC moiety decreased the electron-accepting strength of the end group and increased the intermolecular interactions of ITBTC molecules. As a result, ITBTC exhibited an elevated lowest unoccupied molecular orbital, an improved electron mobility, and a more favorable blend film morphology. Despite its slightly blue-shifted absorption, the photocurrent of ITBTC-based devices was well-maintained due to the extra absorption band in the short wavelength range, which is induced by its conjugation-extended end group. Benefitting from these characteristics, the ITBTC-based solar cells achieved an enhanced power conversion efficiency (PCE) of 10.99% with a simultaneously improved open-circuit voltage (V oc , 0.94 V) and fill factor (FF, 71.3%) and well-maintained short-circuit current density (J sc , 16.37 mA cm −2 ), compared to those of the ITIC-based devices (PCE of 9.53%). These results suggest that extending the π-conjugation of end group through thiophene incorporation is an efficient approach for optimizing both the energy level alignment and intermolecular interaction of the acceptor materials while maintaining their efficient light-harvesting ability. Our study also demonstrates the great potential of the new benzo[b]thiophene-fused end group for constructing high-performance nonfullerene acceptors and provided insight into overcoming the trade-off between J sc and V oc to realize simultaneously enhanced photovoltaic parameters.

Original languageEnglish
Pages (from-to)9822-9830
Number of pages9
JournalJournal of Materials Chemistry A
Volume7
Issue number16
DOIs
Publication statusPublished - 2019 Jan 1

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ASJC Scopus subject areas

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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