Synthesis and Exciton Dynamics of Donor-Orthogonal Acceptor Conjugated Polymers: Reducing the Singlet-Triplet Energy Gap

David M.E. Freeman, Andrew J. Musser, Jarvist M. Frost, Hannah L. Stern, Alexander K. Forster, Kealan J. Fallon, Alexandros G. Rapidis, Franco Cacialli, Iain McCulloch, Tracey M. Clarke, Richard H. Friend, Hugo Bronstein

Research output: Contribution to journalArticlepeer-review

88 Scopus citations

Abstract

The presence of energetically low-lying triplet states is a hallmark of organic semiconductors. Even though they present a wealth of interesting photophysical properties, these optically dark states significantly limit optoelectronic device performance. Recent advances in emissive charge-transfer molecules have pioneered routes to reduce the energy gap between triplets and "bright" singlets, allowing thermal population exchange between them and eliminating a significant loss channel in devices. In conjugated polymers, this gap has proved resistant to modification. Here, we introduce a general approach to reduce the singlet-triplet energy gap in fully conjugated polymers, using a donor-orthogonal acceptor motif to spatially separate electron and hole wave functions. This new generation of conjugated polymers allows for a greatly reduced exchange energy, enhancing triplet formation and enabling thermally activated delayed fluorescence. We find that the mechanisms of both processes are driven by excited-state mixing between π-πand charge-transfer states, affording new insight into reverse intersystem crossing.

Original languageEnglish (US)
Pages (from-to)11073-11080
Number of pages8
JournalJournal of the American Chemical Society
Volume139
Issue number32
DOIs
StatePublished - Aug 16 2017
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry

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