Nanoscale investigation of moisture-induced degradation mechanisms of tris(8-hydroxyquinoline) aluminium-based organic light-emitting diodes

By exploiting tapping mode atomic force microscopy, the moisture-induced degradation mechanisms of ITO (indium tin oxide)-coated glass/CuPc (copper phthalocyanine)/NPB (N, N'-di(naphthalene-1-yl)-N, N'-diphthalbenzidine)/Alq3 (tris(8-hydroxyquinoline) aluminium)-based organic light-emittin...

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Bibliographic Details
Published in:Journal of physics. D, Applied physics Applied physics, 2004-09, Vol.37 (18), p.2618-2622
Main Authors: Xu, M S, Xu, J B, Chen, H Z, Wang, M
Format: Article
Language:English
Subjects:
Applied sciences
Electronics
Exact sciences and technology
Optoelectronic devices
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
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Summary:By exploiting tapping mode atomic force microscopy, the moisture-induced degradation mechanisms of ITO (indium tin oxide)-coated glass/CuPc (copper phthalocyanine)/NPB (N, N'-di(naphthalene-1-yl)-N, N'-diphthalbenzidine)/Alq3 (tris(8-hydroxyquinoline) aluminium)-based organic light-emitting diodes without cathode were investigated. It is found that three types of degradation mechanisms are associated with moisture-exposed Alq3 films, when the device is exposed to moisture, namely, hydration of Alq3, crystallization of Alq3 and reaction of the Alq3 complex with H2O. Crystallization of the NPB layer of ITO/CuPc/NPB was observed on exposure to moisture, and de-wetting simultaneously takes place at the interface of CuPc/NPB. Indium and/or oxygen may diffuse from ITO into the organic layers. These observations provide a clear picture of the moisture-induced degradation mechanisms of the ITO/CuPc/NPB/Alq3-based OLEDs.
ISSN:0022-3727
1361-6463
DOI:10.1088/0022-3727/37/18/019