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Hole injection and transport in a fluorene-containing copolymer

Published online by Cambridge University Press:  11 February 2011

Rizwan U. A. Khan ,
Theo Kreouzis ,
Dmytro Poplavskyy  and
Donal D. C. Bradley
Rizwan U. A. Khan
Affiliation:
Blackett Laboratory, Imperial College London, London SW7 2BW, U.K.
Theo Kreouzis
Affiliation:
Blackett Laboratory, Imperial College London, London SW7 2BW, U.K.
Dmytro Poplavskyy
Affiliation:
Blackett Laboratory, Imperial College London, London SW7 2BW, U.K.
Donal D. C. Bradley
Affiliation:
Blackett Laboratory, Imperial College London, London SW7 2BW, U.K.
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Abstract

We have studied the electrical properties of a fluorene-containing copolymer which is currently being developed for state-of-the-art blue polymer LEDs. This copolymer is made up of three functional groups which are nominally the hole-conducting, electron conducting and emissive regions. Using a combination of current/voltage, time-of-flight and dark injection transient versus temperature measurements, the injection and transport properties of the material have been investigated. Hole injection from polystyrene sulphonate doped polyethylenedioxythiophene (PEDOT:PSS) into the polymer is found to be consistent with an ohmic contact. Hole transport within the fluorene copolymer is found to possess a mobility that is two orders of magnitude lower than that for previously studied polymers containing the copolymer constituents. Using the equations for trap-free space-charge limited current, predicted J/V characteristics have been obtained from the mobility values derived using the time-of-flight technique. We discuss both the reduced hole mobility of the copolymer, and the discrepancies between the measured and predicted J/V characteristics, in terms of variations in both the trap and transport site densities and their energetic and spatial distributions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 734: Symposia A/B – Defect-Mediated Phenomena in Ordered Polymers – Polymer/Metal Interfaces and Defect Mediated Phenomena in Ordered Polymers , 2002 , B6.3
Copyright
Copyright © Materials Research Society 2003

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References

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