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The role of exciplex states in phosphorescent OLEDs with poly(vinylcarbazole) (PVK) host

Jankus, Vygintas; Abdullah, Khalid; Griffiths, Gareth C.; Al-Attar, Hameed; Zheng, Yonghao; Bryce, Martin R.; Monkman, Andrew P.

The role of exciplex states in phosphorescent OLEDs with poly(vinylcarbazole) (PVK) host Thumbnail


Vygintas Jankus

Khalid Abdullah

Gareth C. Griffiths

Hameed Al-Attar

Yonghao Zheng

Andrew P. Monkman


Polymer light emitting diodes (PLEDs) may revolutionize lighting and display industries. PLEDs would enable printing of display or lighting panels on large area substrates that could substantially reduce fabrication costs by avoiding expensive vacuum processes presently used in OLED technologies. PVK is one of the most popular hosts for blue PLEDs. However, PVK has very poor electron transport properties and oxadiazole based electron dopants, e.g. PBD or OXD-7, are used to improve charge transport. This is generally ascribed to capture and transport of electrons on the PBD or OXD-7. Here we show that this is not necessarily the only reason for improved efficiency upon PVK doping. We demonstrate that devices with PVK doped with PBD or OXD-7 have emission lasting up to 1 ms which in some cases may be greater than prompt emission from excitons formed initially on the dopant. This long-lived emission is arising mainly due to formation of an exciplex between the PVK and PBD/OXD-7. This exciplex state then repopulates dopant iridium complexes over a long period of time giving very long-lived emission. We also note that this exciplex-fed long-lived emission from heavy metal complexes is observed in several PLEDs with PBD and PVK (and also OXD-7) doped with blue or green iridium phosphors indicating this to be a general phenomenon.


Jankus, V., Abdullah, K., Griffiths, G. C., Al-Attar, H., Zheng, Y., Bryce, M. R., & Monkman, A. P. (2015). The role of exciplex states in phosphorescent OLEDs with poly(vinylcarbazole) (PVK) host. Organic Electronics, 20, 97-102.

Journal Article Type Article
Acceptance Date Mar 26, 2015
Publication Date May 1, 2015
Deposit Date Mar 26, 2015
Publicly Available Date Mar 31, 2015
Journal Organic Electronics
Print ISSN 1566-1199
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 20
Pages 97-102
Keywords Exciplex, PhOLED, PLED, PVK, PBD, Long-lived emission.


Accepted Journal Article (357 Kb)

Copyright Statement
NOTICE: this is the author’s version of a work that was accepted for publication in Psychology of Organic Electronics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Organic Electronics, 20, May 2015, 10.1016/j.orgel.2015.02.002.

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