Schlüsselwörter
(Englisch)
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organic light-emitting devices; dye doping; polystyrene; poly(vinyl carbazole); luminescence quan-tum yields; single crystal structure; excitons; excimers
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Forschungsprogramme
(Englisch)
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COST-Action 529 - Efficient Lighting for the 21st Century
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Kurzbeschreibung
(Englisch)
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This project targets the efficiency improvement of polymer light emitting devices by investigating doping of conjugated electroluminescent polymers. For this purpose, fluorescent conjugated molecules that do not present concentration quenching will be used. It is the aim to study the physico-chemical mechanisms under device operation and to address stability issues.
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Weitere Hinweise und Angaben
(Englisch)
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Full name of research-institution/enterprise: Eidg. Materialprüfungs- und Forschungsanstalt EMPA Abt 140
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Partner und Internationale Organisationen
(Englisch)
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AT, BE, BG, CH, CZ, DE, ES, FI, FR, GR, HR, HU, IT, LT, LV, NL, PT, RO, SE, UK
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Abstract
(Englisch)
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Molecular doping of electroluminescent devices is one of the numerous routes to achieve cheap, efficient organic light emitting diodes (OLEDs). Whilst the operating mechanism of small molecule OLEDs is well understood, little knowledge is available regarding the role of dopant in the perform-ance of polymer light emitting devices. In most cases, the level of doping concentration of the lumi-nescent dye in the host matrix is limited by the dye self quenching. In order to circumvent this draw-back, we have synthesised a cyano-susbtituted oligo-phenylenevinylene oligomer (CN-OPV) that retains its luminescent properties in the solid state up to high concentrations. The photophysics of the pure dye in the solid (evaporated film), solution and aggregated state as blends in host matrixes (such as polystyrene and polyvinylcarbazole) and as nanoparticles are in-vestigated by fluorescence spectroscopy, solid sate quantum yield measurements, X ray single crystal analysis, powder diffraction and optical microscopy. On the other hand, the dye is successfully incorporated in the two host matrixes with loadings rang-ing from 0.1 to 20% dye ratio to fabricate single layer polymer OLEDs. It is demonstrated that rather efficient OLEDs can be produced by this simple blending method using cheap polymers. At the con-centration used, charge carriers are able to hop from one doping molecule to the other. Thin film annealing studies are also undertaken to study the diffusion behaviour of the dye in both matrices. These studies give an insight into the possible long term degradation mechanisms of the fabricated devices.
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Datenbankreferenzen
(Englisch)
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Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. +41 31 322 74 82 Swiss Project-Number: C04.0090
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