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On the origin of exciton formation in dye doped Alq3 OLEDs.

Gomez, J A*; Castro, F A; Nuumlesch, F*; Zuppiroli, L*; Graeff, C F O* (2012) On the origin of exciton formation in dye doped Alq3 OLEDs. Appl. Phys. A: Mater. Sci. Process., 108 (3). pp. 727-731.

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Electrically Detected Magnetic Resonance (EDMR) was used to investigate the influence of dye doping on spin-dependent exciton formation in Aluminum (III) 8-hydroxyquinoline (Alq3) based Organic Light Emitting Diodes (OLEDs) with different device structures. 4- (dicyanomethylene)-2-methyl-6-f 2-[(4-diphenylamino)- phenyl]ethylg-4H-pyran (DCM-TPA) and 5,6,11,12-
tetraphenylnaphthacene (Rubrene) were used as dopants. Results at room temperature show significant differences on the EDMR spectra (g-factor and linewidth) of doped and undoped devices. Signals from DCM-TPA and Rubrene dye doped OLEDs showed strong temperature dependence, with signal intensity increasing by 2 orders of magnitude below 200K for DCM-TPA dye doped OLEDs and increasing by 1 order of magnitude below 225 K for the Rubrene dye doped device, while undoped devices
shows almost no temperature dependence. By adding a spacer layer of undoped Alq3 at the recombination zone, changes in bias voltage were used to shift the recombination from doped to undoped region and correlate that with changes in the EDMR spectrum. Our results are clear evidence that charge trapping on the dopant followed by recombination is the main mechanism of light emission for the investigated materials.

Item Type: Article
Keywords: Exciton formation, Dye Doped OLEDs, Alq3, DCM-TPA, Rubrene, EDMR
Subjects: Advanced Materials
Advanced Materials > Electrochemistry
Identification number/DOI: 10.1007/s00339-012-6957-8
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/5527

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