Dynamics of singlet fission and electron injection in self-assembled acene monolayers on titanium dioxide

Natalie A. Pace, Dylan H. Arias, Devin B. Granger, Steven Christensen, John E. Anthony, Justin C. Johnson

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36 Scopus citations

Abstract

We employ a combination of linear spectroscopy, electrochemistry, and transient absorption spectroscopy to characterize the interplay between electron transfer and singlet fission dynamics in polyacene-based dyes attached to nanostructured TiO2. For triisopropyl silylethynyl (TIPS)-pentacene, we find that the singlet fission time constant increases to 6.5 ps on a nanostructured TiO2 surface relative to a thin film time constant of 150 fs, and that triplets do not dissociate after they are formed. In contrast, TIPS-tetracene singlets quickly dissociate in 2 ps at the molecule/TiO2 interface, and this dissociation outcompetes the relatively slow singlet fission process. The addition of an alumina layer slows down electron injection, allowing the formation of triplets from singlet fission in 40 ps. However, the triplets do not inject electrons, which is likely due to a lack of sufficient driving force for triplet dissociation. These results point to the critical balance required between efficient singlet fission and appropriate energetics for interfacial charge transfer.

Original languageEnglish
Pages (from-to)3004-3013
Number of pages10
JournalChemical Science
Volume9
Issue number11
DOIs
StatePublished - 2018

Bibliographical note

Funding Information:
N. A. P., D. H. A., S. C. and J. C. J. acknowledge the Solar Photochemistry Program supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences, and Geosciences under Contract No. DEAC36- 08GO28308 with NREL for support of transient absorption and steady-state spectroscopy, ALD, and electrochemistry. D. B. G. and J. E. A. thank the National Science Foundation (DMREF-1627428) for support of acene synthesis.

Funding Information:
The authors would like to thank Thomas J. Carey and Niels H. Damrauer for providing our TIPS Tc compound, Nedezhda V. Korovina for assistance with sample preparation for sensitization experiments, Mike Carroll for assistance with SEC measurements, and Garry Rumbles for stimulating discussions. N. A. P. and D. H. A. prepared and characterized solution and lm samples, performed TA spectroscopy, and analyzed the data under the guidance of J. C. J. S. C. deposited alumina on TiO2 samples. D. B. G. synthesized TIPS Pc COOH and TIPS Tc COOH under the guidance of J. E. A. N. A. P. and D. H. A. wrote the manuscript with input from all the authors. N. A. P., D. H. A., S. C. and J. C. J. acknowledge the Solar Photochemistry Program supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences, and Geosciences under Contract No. DE-AC36-08GO28308 with NREL for support of transient absorption and steady-state spectroscopy, ALD, and electrochemistry. D. B. G. and J. E. A. thank the National Science Foundation (DMREF-1627428) for support of acene synthesis.

Publisher Copyright:
© 2018 The Royal Society of Chemistry.

ASJC Scopus subject areas

  • Chemistry (all)

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