Influence of carrier injection on the electromodulation response of trap-rich polymer light-emitting diodes

P. J. Brewer, A. J. Demello, J. C. Demello, P. A. Lane, D. D.C. Bradley, R. Fletcher, J. O'brien

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18 Scopus citations

Abstract

We investigate the influence of carrier injection on the electric field distribution in polyfluorene-based polymer light-emitting diodes containing poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). The devices show strong charge-induced electromodulation spectra due to the accumulation of trapped electrons close to the PEDOT:PSS/polyfluorene interface. The trapped electrons cause the potential to drop preferentially at the interface, enhancing hole injection and substantially reducing the magnitude of the electric field in the bulk semiconductor. The detailed operating mechanisms of such "trap-rich" devices are poorly understood, and in this paper we perform a series of temperature-dependent current-voltage sweeps and electromodulation measurements to clarify the role of the injected charge. We find that the devices show strong field redistribution only at room temperature and that devices operating at lower temperatures (
Original languageEnglish (US)
JournalJournal of Applied Physics
Volume99
Issue number11
DOIs
StatePublished - Jun 1 2006
Externally publishedYes

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