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Proceedings Paper

Cyclooctatetrene derivatives as electron transporters and hole blocker in organic LEDs
Author(s): Haiping Hong; Peter Djurovich; Mark E. Thompson; Ping Lu; William P. Weber
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Paper Abstract

In this paper, we report that novel tetraphenyl- tetraalkynyl-COTs and octaaryl-COTs can be used as electron transport and hole blocker layer in organic LEDs. These materials have the similar reduction potentials compared to traditional electron transporters, such as Alq3. The energy gaps for all of the COT derivatives studied here are very wide (> 3 eV), making it possible to fabricate blue emitting OLEDs with these materials. We have fabricated devices of the structure ITO/NPD400 angstrom/COT-Me 400 angstrom/Mg-Ag. (ITO equals indium-tin-oxide, NPD equals N,N'-diphenyl-N,N'-dinapthylbenzidine). The external quantum yield reaches 0.15% and the emission comes from NPD ((lambda) max equals 436 nm). When 1% perylene (by weight) is doped into the NPD, the (lambda) max of emission shifts to the 454 nm with the external QE reaches 0.60%. It indicates the efficient energy transfer from NPD to perylene. Changing the COT layer thickness from 400 Angstrom to 200 Angstrom, the emission is still from the NPD layer, as seen before. However, the I-V curve and turn-on voltage both shift to lower potentials by ca 2 - 3 V with the QE drops to 0.06%. The device QE can be increased by either using thin Alq layer or replacing Mg:Ag with LiF/Al electrode. Finally, the devices using COTs as hole blocker are fabricated and results are discussed.

Paper Details

Date Published: 2 February 2001
PDF: 10 pages
Proc. SPIE 4105, Organic Light-Emitting Materials and Devices IV, (2 February 2001); doi: 10.1117/12.416920
Show Author Affiliations
Haiping Hong, Univ. of Southern California (United States)
Peter Djurovich, Univ. of Southern California (United States)
Mark E. Thompson, Univ. of Southern California (United States)
Ping Lu, Univ. of Southern California (China)
William P. Weber, Univ. of Southern California (United States)

Published in SPIE Proceedings Vol. 4105:
Organic Light-Emitting Materials and Devices IV
Zakya H. Kafafi, Editor(s)

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