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Triazatruxene: A Rigid Central Donor Unit for a D–A3 Thermally Activated Delayed Fluorescence Material Exhibiting Sub‐Microsecond Reverse Intersystem Crossing and Unity Quantum Yield via Multiple Singlet–Triplet State Pairs

Lookup NU author(s): Dr Julien EngORCiD, Professor Thomas Penfold



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


By inverting the common structural motif of thermally activated delayed fluorescence materials to a rigid donor core and multiple peripheral acceptors, reverse intersystem crossing (rISC) rates are demonstrated in an organic material that enables utilization of triplet excited states at faster rates than Ir-based phosphorescent materials. A combination of the inverted structure and multiple donor–acceptor interactions yields up to 30 vibronically coupled singlet and triplet states within 0.2 eV that are involved in rISC. This gives a significant enhancement to the rISC rate, leading to delayed fluorescence decay times as low as 103.9 ns. This new material also has an emission quantum yield ≈ 1 and a very small singlet–triplet gap. This work shows that it is possible to achieve both high photoluminescence quantum yield and fast rISC in the same molecule. Green organic light-emitting diode devices with external quantum efficiency > 30% are demonstrated at 76 cd m−2 .

Publication metadata

Author(s): dos Santos PL, Ward JS, Congrave DG, Batsanov AS, Eng J, Stacey JE, Penfold TJ, Monkman AP, Bryce MR

Publication type: Article

Publication status: Published

Journal: Advanced Science

Year: 2018

Volume: 5

Issue: 6

Print publication date: 01/06/2018

Online publication date: 16/04/2018

Acceptance date: 01/02/2018

Date deposited: 17/04/2018

ISSN (electronic): 2198-3844

Publisher: Wiley


DOI: 10.1002/advs.201700989


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