Spectroscopic Ellipsometry Study of Organic Light Emitting Diode Based on Phosphorescent PtOEP

Taiju TSUBOI  Yoko WASAI  Nataliya NABATOVA-GABAIN  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E87-C   No.12   pp.2039-2044
Publication Date: 2004/12/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Organic Molecular Electronics)
Category: Characterization and Abilities of Organic Electronic Devices
Keyword: 
organic light emitting diodes,  spectroscopic ellipsometry,  optical constants,  layer thickness,  PtOEP,  

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Summary: 
We have determined the thickness and optical constants (refractive index and extinction coefficient) of each layer in the multi-layer organic light emitting diode (OLED) devices based on phosphorescent platinum octaethyl porphine (PtOEP) using a phase modulated spectroscopic ellipsometer. The thickness of each layer estimated from the ellipsometric measurement is different from the thickness measured with quartz oscillator during the evaporation of organic materials. The deviation of total multi-layer thickness is about 5%, while the deviation in each of N, N'-bis(1-naphtyl)-N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) and aluminum tris 8-hydroxyquinoline (Alq3) layers is about 20-25%. Additionally the spectra of refractive index and extinction coefficient of Alq3 and α-NPD layers are different from those that are measured using the single layer films. These results are understood by penetration of organic material from the neighboring layers in the multi-layer structure devices.