Applied Physics Letters · 2001 · 109 citations · 19 references
Natural SciencesChemistryMaterials ScienceElectronic MaterialsPolymer ChemistryPolymer MaterialsConducting PolymersConductive PolymersOptical PolymersOrganic SemiconductorsPolymer DegradationPolymer StabilityDegradationDye DegradationPhosphorescent MaterialsPhosphorescent PolymersPolymer Degradation MechanismsPolymer Light-emitting DiodesStability DegradationVoltammetry
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.
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