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Lookup NU author(s): Professor Thomas Penfold, Dr Julien EngORCiD
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 (TADF) materials to a rigid donor core and multiple peripheral acceptors, it has been shown possible to achieve both a reverse intersystem crossing (rISC) rate > 1°ø107 s−1 and a unity photoluminescence quantum yield [Dos Santos et al. Adv. Sci. 5 (2018) 1700989]. However, the rISC rate in this motif is quenched by localisation of the excited state electronic structure which causes in-equivalence between the peripheral acceptors. In this paper, we explore a series of related molecular targets which seek to reduce the effect of localisation on the rISC rates. This includes structures that contain donors exhibiting three-fold or four-fold symmetry and different degrees of steric hindrance around the donor-acceptor bond with the objective of using steric hindrance to exert finer conformational control of the excited state dynamics to enhance functional properties. We demonstrate that a triazatruxene central donor is most effective for TADF owing to the energetic position of the locally excited state, while cyanobenzonitriles are the most effective acceptors for reducing the effect of localisation on the electronic structure. These also push the emission into the blue region of the spectrum, opening the possibilities for this to be a pathway to develop efficient blue TADF emitters.
Author(s): Penfold TJ, Eng J
Publication type: Article
Publication status: Published
Journal: ChemPhotoChem
Year: 2022
Volume: 7
Issue: 3
Print publication date: 01/03/2023
Online publication date: 07/11/2022
Acceptance date: 07/11/2022
Date deposited: 08/11/2022
ISSN (electronic): 2367-0932
Publisher: Wiley
URL: https://doi.org/10.1002/cptc.202200243
DOI: 10.1002/cptc.202200243
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