TITLE

Degradation mechanism of phosphorescent-dye-doped polymer light-emitting diodes

AUTHOR(S)
Chang, Shun-Chi; He, Gufeng; Chen, Fang-Chung; Guo, Tzung-Fang; Yang, Yang
PUB. DATE
September 2001
SOURCE
Applied Physics Letters;9/24/2001, Vol. 79 Issue 13
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The degradation mechanism of phosphorescent-dye-doped polymer light-emitting diodes (PLEDs) is investigated. The active medium of our PLED is a polymer blend comprising poly(vinylcarbazole) (PVK), [2-(4-biphenylyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole] (t-PBD), and platinum(II)-2,8,12,17-tetraethyl-3,7,13,18-tetramethylporphyrin (PtOX). The cyclic voltammetry result shows that the reductive reversibility of PtOX is poor. This result suggests that PLED doped with PtOX is not stable if PtOXs trap electrons and turn into anionic PtOX species. This was indeed verified by fabricating single-layer PLEDs with various amounts of electron-transporting material, t-PBD. A slower degradation rate was observed from the devices with higher concentration of t-PBD, because of the reduction of the electron accumulation at the PtOX sites. The half decay lifetime of our phosphorescent polymer LED has been improved by a factor of ∼40, from 1.2 to 45 h. © 2001 American Institute of Physics.
ACCESSION #
5193852

 

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