Persistent Dimer Emission in Thermally Activated Delayed Fluorescence Materials

Etherington, Marc K.; Kukhta, Nadzeya A.; Higginbotham, Heather F.; Danos, Andrew; Bismillah, Aisha N.; Graves, David R.; McGonigal, Paul R.; Haase, Nils; Morherr, Antonia; Batsanov, Andrei S.; Pflumm, Christof; Bhalla, Vandana; Bryce, Martin R.; Monkman, Andrew P.

Abstract

We expose significant changes in emission color of carbazole-based thermally activated delayed fluorescence (TADF) emitters that arise through the presence of persistent dimer states in thin films and organic light-emitting diodes(OLEDs). Direct photoexcitation of this dimer state in 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) reveals the significant influence of dimer species on the color purity of its photoluminescence and electroluminescence. The dimer species is sensitive to the sample preparation method and its enduring presence contributes to the widely reported concentration-mediated redshift in the photoluminescence and electroluminescence of evaporated thin films. This discovery has significant implications on the usability of these, and similar, molecules for OLEDs and explains disparate electroluminescence spectra presented in the literature for these compounds. The significant dimerization-controlled changes observed in the TADF process and photoluminescence efficiency mean that careful consideration of dimer states is imperative in the design of future TADF emitters and the interpretation of previously reported studies of carbazole-based TADF materials.

Citation

Etherington, M. K., Kukhta, N. A., Higginbotham, H. F., Danos, A., Bismillah, A. N., Graves, D. R., …Monkman, A. P. (2019). Persistent Dimer Emission in Thermally Activated Delayed Fluorescence Materials. Journal of Physical Chemistry C, 123(17), 11109-11117. https://doi.org/10.1021/acs.jpcc.9b01458

• Journal Article Type: Article
• Acceptance Date: Apr 3, 2019
• Online Publication Date: Apr 3, 2019
• Publication Date: May 2, 2019
• Deposit Date: Apr 3, 2019
• Publicly Available Date: May 2, 2019
• Journal: Journal of Physical Chemistry C
• Print ISSN: 1932-7447
• Electronic ISSN: 1932-7455
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 123
• Issue: 17
• Pages: 11109-11117
• DOI: https://doi.org/10.1021/acs.jpcc.9b01458
• Public URL: https://durham-repository.worktribe.com/output/1304621