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The Importance of Vibronic Coupling for Efficient Reverse Intersystem Crossing in TADF molecules

Lookup NU author(s): Jamie Gibson, Professor Thomas Penfold

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Abstract

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.

Publication metadata

Author(s): Gibson J, Monkman AP, Penfold TJ

Publication type: Article

Publication status: Published

Journal: ChemPhysChem

Year: 2016

Volume: 17

Issue: 19

Pages: 2956-2961

Print publication date: 05/10/2016

Online publication date: 24/06/2016

Acceptance date: 21/06/2016

Date deposited: 24/06/2016

ISSN (print): 1439-4235

ISSN (electronic): 1439-7641

Publisher: Wiley - VCH Verlag GmbH & Co. KGaA

URL: http://dx.doi.org/10.1002/cphc.201600662

DOI: 10.1002/cphc.201600662

Data Access Statement: http://dx.doi.org/10.17634/153015-1

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