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

Shun Chi Chang*, Gufeng He, Fang-Chung Chen, Tzung Fang Guo, Yang Yang

*Corresponding author for this work

Research output: Contribution to journalArticle

107 Scopus citations

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.

Original languageEnglish
Pages (from-to)2088-2090
Number of pages3
JournalApplied Physics Letters
Volume79
Issue number13
DOIs
StatePublished - 24 Sep 2001

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