Cyclooctatetrene derivatives as electron transporters and hole blocker in organic LEDs

Haiping Hong; Peter Djurovich; Mark E. Thompson; Ping Lu; William P. Weber

doi:10.1117/12.416920

2 February 2001 Cyclooctatetrene derivatives as electron transporters and hole blocker in organic LEDs

Haiping Hong, Peter Djurovich, Mark E. Thompson, Ping Lu, William P. Weber

Proceedings Volume 4105, Organic Light-Emitting Materials and Devices IV; (2001) https://doi.org/10.1117/12.416920
Event: International Symposium on Optical Science and Technology, 2000, San Diego, CA, United States

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.

Citation Download Citation

Haiping Hong, Peter Djurovich, Mark E. Thompson, Ping Lu, and William P. Weber "Cyclooctatetrene derivatives as electron transporters and hole blocker in organic LEDs", Proc. SPIE 4105, Organic Light-Emitting Materials and Devices IV, (2 February 2001); https://doi.org/10.1117/12.416920

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