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Materials Engineering For Polarized Light Emitting Diodes

Published online by Cambridge University Press:  10 February 2011

G. Wegner ,
D. Neher ,
M. Remmers ,
V. Cimrova  and
M. Schulze
G. Wegner
Affiliation:
Max-Planck-Institut f. Polymerforschung, P.O. Box 3148, D-55021 Mainz, Germany
D. Neher
Affiliation:
Max-Planck-Institut f. Polymerforschung, P.O. Box 3148, D-55021 Mainz, Germany
M. Remmers
Affiliation:
Max-Planck-Institut f. Polymerforschung, P.O. Box 3148, D-55021 Mainz, Germany
V. Cimrova
Affiliation:
Max-Planck-Institut f. Polymerforschung, P.O. Box 3148, D-55021 Mainz, Germany
M. Schulze
Affiliation:
Max-Planck-Institut f. Polymerforschung, P.O. Box 3148, D-55021 Mainz, Germany
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Abstract

Electroluminescent devices have been made from organo-soluble derivatives of poly(pphenylene). Solubility and processibility by the LB-technique is achieved by attaching alkoxy side groups to the backbone-p-phenylene units. These polymers are of the hairy-rod (HR) type. If transferred as monolayers from the air-water-interface, monodomain multilayers with large order parameters of chain orientation are obtained. A 130 nm thick LB-film of poly(2,5-diisopentoxy-pphenylene) shows blue photoluminescence at λmax = 3.08 eV (404 nm) with a tail extending to 2 eV. The anisotropy was (lII- l1)/ (l11, + l11)= 0.5. This LB-film between a transparent gold and an evaporated Al-electrode shows polarized light emission at E ≤ 6.107 V cm−1 with am=a λmax2.2 eV and an in-plane anisotropy of 0.54. Thin films obtained by spincoating of the same polymer show isotropic electroluminescence between ITO and Al-electrodes with an external quantum efficiency of about 0.03 %. Higher efficiencies up to 4 % were realized optimizing the device architecture and the electrodes. Photocrosslinkable sites are introduced as side groups to the poly(pphenylene) chain. This allows patterning of the LEDs. General features of the supramolecular architecture and typical defect structures occurring in films of polyconjugated macromolecules are discussed using prototypical polymers as examples. Important effects are chain segregation according to chain length and formation of disclinations.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 413: Symposium W – Electrical, Optical, and Magnetic Properties of Organic Solid State Materials III , 1995 , 23
Copyright
Copyright © Materials Research Society 1996

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References

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