Issue 22, 2019

Enhanced thermally activated delayed fluorescence through bridge modification in sulfone-based emitters employed in deep blue organic light-emitting diodes

Abstract

Two thermally activated delayed fluorescence (TADF) emitters bearing a new dipyridylsulfone core as the electron-accepting unit and di-tert-butyl carbazoles as electron-donating units are reported. The two emitters, pDTCz-2DPyS and pDTCz-3DPyS, differ in the regiochemistry of the substitution about the pyridine rings [pDTCz-2DPyS = 9,9′-(sulfonylbis(pyridine-6,3-diyl))bis(3,6-di-tert-butyl-9H-carbazole); pDTCz-3DPyS = 9,9′-(sulfonylbis(pyridine-5,2-diyl))bis(3,6-di-tert-butyl-9H-carbazole)]. Both compounds show blue emission in the range of 450–465 nm, which is in line with theoretical calculations. They have very similar singlet–triplet energy (ΔEST) gaps (ΔEST = 0.22 eV and 0.21 eV for pDTCz-3DPyS and pDTCz-2DPyS, respectively). pDTCz-2DPyS has a much larger proportion of delayed emission (26.2%) than pDTCz-3DPyS (1.2%). The two compounds show comparable photoluminescence quantum yields of 60% in 2,8-bis(diphenylphosphoryl)dibenzo[b,d]thiophene (PPT) doped films. The performance of organic light-emitting diodes (OLEDs) depends on the host used. The maximum external quantum efficiency (EQE) in the PPT host of pDTCz-3DPyS is 7.0%, whilst for pDTCz-2DPyS it is 12.4%. High performance is obtained for both materials when bis[2-(diphenylphosphino)phenyl]ether oxide (DPEPO) is used as the host, with a maximum EQE of 13.4% for pDTCz-3DPyS and 11.4% for pDTCz-2DPyS, which is a significant improvement from 4.6% for the reference pDTCz-DPS. In addition, pDTCz-3DPyS shows pure blue electroluminescence with CIE color coordinates of (0.15, 0.12) compared to pDTCz-2DPyS with coordinates of (0.15, 0.19).

Graphical abstract: Enhanced thermally activated delayed fluorescence through bridge modification in sulfone-based emitters employed in deep blue organic light-emitting diodes

Supplementary files

Article information

Article type
Paper
Submitted
20 mar 2019
Accepted
23 apr 2019
First published
23 apr 2019

J. Mater. Chem. C, 2019,7, 6664-6671

Enhanced thermally activated delayed fluorescence through bridge modification in sulfone-based emitters employed in deep blue organic light-emitting diodes

P. Rajamalli, D. Chen, W. Li, I. D. W. Samuel, D. B. Cordes, A. M. Z. Slawin and E. Zysman-Colman, J. Mater. Chem. C, 2019, 7, 6664 DOI: 10.1039/C9TC01498E

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