Lookup NU author(s): Jamie Gibson,
Dr Thomas Penfold
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Factors influencing the rate of reserve intersystem crossing (k_rISC) in thermally activated delayed fluorescence (TADF) emitters are critical for improving the efficiency and performance of 3rd 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 k_rISC. 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 k_rISC by 4 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.
Author(s): Gibson J, Monkman AP, Penfold TJ
Publication type: Article
Publication status: Published
Print publication date: 05/10/2016
Online publication date: 24/06/2016
Acceptance date: 21/06/2016
ISSN (print): 1439-4235
ISSN (electronic): 1439-7641
Publisher: Wiley - VCH Verlag GmbH & Co. KGaA
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