Vibronically coherent ultrafast triplet-pair formation and subsequent thermally activated dissociation control efficient endothermic singlet fission

Hannah L. Stern, Alexandre Cheminal, Shane R. Yost, Katharina Broch, Sam L. Bayliss, Kai Chen, Maxim Tabachnyk, Karl Thorley, Neil Greenham, Justin M. Hodgkiss, John Anthony, Martin Head-Gordon, Andrew J. Musser, Akshay Rao, Richard H. Friend

Research output: Contribution to journalArticlepeer-review

177 Scopus citations

Abstract

Singlet exciton fission (SF), the conversion of one spin-singlet exciton (S 1) into two spin-triplet excitons (T 1), could provide a means to overcome the Shockley-Queisser limit in photovoltaics. SF as measured by the decay of S 1 has been shown to occur efficiently and independently of temperature, even when the energy of S 1 is as much as 200 meV less than that of 2T 1. Here we study films of triisopropylsilyltetracene using transient optical spectroscopy and show that the triplet pair state (TT), which has been proposed to mediate singlet fission, forms on ultrafast timescales (in 300 fs) and that its formation is mediated by the strong coupling of electronic and vibrational degrees of freedom. This is followed by a slower loss of singlet character as the excitation evolves to become only TT. We observe the TT to be thermally dissociated on 10-100 ns timescales to form free triplets. This provides a model for â € temperature-independent' efficient TT formation and thermally activated TT separation.

Original languageEnglish
Pages (from-to)1205-1212
Number of pages8
JournalNature Chemistry
Volume9
Issue number12
DOIs
StatePublished - Dec 1 2017

Bibliographical note

Publisher Copyright:
© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering

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