Issue 34, 2019

The effect of a heavy atom on the radiative pathways of an emitter with dual conformation, thermally-activated delayed fluorescence and room temperature phosphorescence

Abstract

This study focuses on the photophysics of a donor–acceptor molecule with 2,4,6-triphenyl-1,3,5-triazine and phenoselenazine acceptor and donor units. Selenium distinctively folds the phenoselenazine resulting in the appearance of two conformers, yielding both room temperature phosphorescence (RTP) and thermally-activated delayed fluorescence (TADF). This combination produces a unique in-depth picture of the mechanisms inherent to dual emission in TADF molecules. We revisit the photophysics of the phenothiazine analogue and observe similar behaviours. The dual emission comes from a short-lifetime quasi-axial conformer and longer-lifetime quasi-equatorial conformer giving efficient TADF. The quasi-axial conformer is not TADF active because it has a low energy local triplet that quenches the charge transfer states, giving rise to RTP. From sulphur to selenium, we point to an enhancement in the phosphorescence radiative decay with little effect on the reverse intersystem crossing (rISC) which means that adding a heavy atom to the donor does not affect the TADF performance. The interplay between TADF and RTP leads to yellow-green emitting devices with external quantum efficiencies of 17% from the optimisation of the conformer that gives rise to TADF. Therefore, the subtle effects enhanced by the phenoselenazine donor further add to our knowledge about how the molecular structure affects TADF photophysics.

Graphical abstract: The effect of a heavy atom on the radiative pathways of an emitter with dual conformation, thermally-activated delayed fluorescence and room temperature phosphorescence

Supplementary files

Article information

Article type
Paper
Submitted
10 May 2019
Accepted
10 Jul 2019
First published
11 Jul 2019

J. Mater. Chem. C, 2019,7, 10481-10490

The effect of a heavy atom on the radiative pathways of an emitter with dual conformation, thermally-activated delayed fluorescence and room temperature phosphorescence

D. de Sa Pereira, D. R. Lee, N. A. Kukhta, K. H. Lee, C. L. Kim, A. S. Batsanov, J. Y. Lee and A. P. Monkman, J. Mater. Chem. C, 2019, 7, 10481 DOI: 10.1039/C9TC02477H

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements