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Internal Field Distribution in Organic Light Emitting Diodes with Double Layer Structure

Published online by Cambridge University Press:  10 February 2011

C. Hochfilzer
Affiliation:
Institute for Solid State Physics, University of Technology Graz, 8010 Graz, Austria
T. Jost
Affiliation:
Institute for Solid State Physics, University of Technology Graz, 8010 Graz, Austria
A. Niko
Affiliation:
Institute for Solid State Physics, University of Technology Graz, 8010 Graz, Austria
W. Graupner
Affiliation:
Institute for Solid State Physics, University of Technology Graz, 8010 Graz, Austria
G. Leising
Affiliation:
Institute for Solid State Physics, University of Technology Graz, 8010 Graz, Austria
C. W. Tang
Affiliation:
Imaging Research and Advanced Development, Eastman Kodak Co., Rochester, NY 14650
E. Forsythe
Affiliation:
Department of Physics and Astronomy, University of Rochester, NY14627
Y. Gao
Affiliation:
Department of Physics and Astronomy, University of Rochester, NY14627
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Abstract

Double layer organic light emitting devices (OLED) are constructed by evaporating tris(8 -hydroxy) quinoline aluminum (Alq3) on a spin cast thin film of a methyl substituted ladder type poly -para -phenylene (m -LPPP). A thick layer of Mg:Ag is used as the cathode material. These organic materials are very suitable for application in OLEDs both, as transporting materials as well as active layers. Alq3 predominantly transports electrons while m - LPPP is a conjugated polymer having higher hole mobilities. Due to these transport properties the formation and radiative recombination of the excitons in ITO/m -LPPP/Alq3/Mg:Ag devices occur close to the m -LPPP/Alq3 interface. We compare the device performance of OLEDs with varying Alq3 layer thickness (0, 50, 150, 300, 500Å) and constant m -LPPP layer thickness (900Å). A difference in the device parameters and performance as a function of the Alq3 layer thickness is observed. We analyze these results with respect to the internal electric field distribution of the double layer devices derived from electroabsorption measurements.

Type
Research Article
Copyright
Copyright © Materials Research Society 1998

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