The Importance of Vibronic Coupling for Efficient Reverse Intersystem Crossing in Thermally Activated Delayed Fluorescence Molecules

Gibson, J.; Monkman, A.P.; Penfold, T.

doi:10.1002/cphc.201600662

The Importance of Vibronic Coupling for Efficient Reverse Intersystem Crossing in Thermally Activated Delayed Fluorescence Molecules

Gibson, J.; Monkman, A.P.; Penfold, T.

Authors

J. Gibson

Professor Andrew Monkman a.p.monkman@durham.ac.uk
Professor

T. Penfold

Abstract

Factors influencing the rate of reverse intersystem crossing (krISC) in thermally activated delayed fluorescence (TADF) emitters are critical for improving the efficiency and performance of third-generation heavy-metal-free organic light-emitting diodes (OLEDs). However, present understanding of the TADF mechanism does not extend far beyond a thermal equilibrium between the lowest singlet and triplet states and consequently research has focused almost exclusively on the energy gap between these two states. Herein, we use a model spin-vibronic Hamiltonian to reveal the crucial role of non-Born-Oppenheimer effects in determining krISC. We demonstrate that vibronic (nonadiabatic) coupling between the lowest local excitation triplet (3LE) and lowest charge transfer triplet (3CT) opens the possibility for significant second-order coupling effects and increases krISC by about four orders of magnitude. Crucially, these simulations reveal the dynamical mechanism for highly efficient TADF and opens design routes that go beyond the Born-Oppenheimer approximation for the future development of high-performing systems.

Citation

Gibson, J., Monkman, A., & Penfold, T. (2016). The Importance of Vibronic Coupling for Efficient Reverse Intersystem Crossing in Thermally Activated Delayed Fluorescence Molecules. ChemPhysChem, 17(19), 2956-2961. https://doi.org/10.1002/cphc.201600662

Journal Article Type	Article
Online Publication Date	Jul 26, 2016
Publication Date	Oct 5, 2016
Deposit Date	Jan 18, 2017
Publicly Available Date	Apr 21, 2017
Journal	ChemPhysChem
Print ISSN	1439-4235
Electronic ISSN	1439-7641
Publisher	Wiley
Peer Reviewed	Peer Reviewed
Volume	17
Issue	19
Pages	2956-2961
DOI	https://doi.org/10.1002/cphc.201600662

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©2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.