Site-selective measurement of coupled spin pairs in an organic semiconductor

S. L. Bayliss, L. R. Weiss, A. Mitioglu, K. Galkowski, Z. Yang, K. Yunusova, A. Surrente, K. J. Thorley, J. Behrends, R. Bittl, J. E. Anthony, A. Rao, R. H. Friend, P. Plochocka, P. C.M. Christianen, N. C. Greenham, A. D. Chepelianskii

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

From organic electronics to biological systems, understanding the role of intermolecular interactions between spin pairs is a key challenge. Here we show how such pairs can be selectively addressed with combined spin and optical sensitivity. We demonstrate this for bound pairs of spin-triplet excitations formed by singlet fission, with direct applicability across a wide range of synthetic and biological systems. We show that the site sensitivity of exchange coupling allows distinct triplet pairs to be resonantly addressed at different magnetic fields, tuning them between optically bright singlet (S = 0) and dark triplet quintet (S = 1, 2) configurations: This induces narrow holes in a broad optical emission spectrum, uncovering exchange-specific luminescence. Using fields up to 60 T, we identify three distinct triplet-pair sites, with exchange couplings varying over an order of magnitude (0.3–5 meV), each with its own luminescence spectrum, coexisting in a single material. Our results reveal how site selectivity can be achieved for organic spin pairs in a broad range of systems.

Original languageEnglish
Pages (from-to)5077-5082
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number20
DOIs
StatePublished - May 15 2018

Bibliographical note

Publisher Copyright:
© 2018 National Academy of Sciences. All Rights Reserved.

Keywords

  • Exchange coupling
  • Organic semiconductors
  • Organic spintronics
  • Singlet fission
  • Triplet excitons

ASJC Scopus subject areas

  • General

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