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Proceedings Paper

Photoresponse and electroresponse of polymer light-emitting diodes
Author(s): Z. Valy Vardeny; Xing Wei; Stefan A. Jeglinski
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Paper Abstract

We have studied the photoresponse and electroresponse of light emitting diodes (LEDs) made from a variety of soluble conducting polymers sandwiched between indium tin oxide (ITO) and metals including calcium, aluminum and copper. Under illumination all freshly prepared LEDs exhibit relatively large photoconductive current-voltage (I-V) responses which cross the dark I-V curve at a forward-bias voltage V0 that scales with the difference in the work functions between the ITO and metal electrodes. This causes the open-circuit voltage to easily saturate at V0 and consequently to be temperature independent, in contrast to the properties of the photovoltaic effect exhibited by conventional Schottky-barrier type photodiodes. Some LEDs, prepared under less ideal conditions exhibit I-V curve, electroluminescence (EL) intensity-voltage (IEL-V) curve, an EL spectra identical in forward and reverse bias. The I-V curves were also symmetric under illumination, with I approximately equal to 0 at V equals 0, suggesting a negligibly small internal electric field. These diodes are discussed in relation to Fermi-level pinning at defect states in the interfaces between the polymer and the electrodes.

Paper Details

Date Published: 15 September 1995
PDF: 10 pages
Proc. SPIE 2528, Optical and Photonic Applications of Electroactive and Conducting Polymers, (15 September 1995); doi: 10.1117/12.219551
Show Author Affiliations
Z. Valy Vardeny, Univ. of Utah (United States)
Xing Wei, Univ. of Utah (United States)
Stefan A. Jeglinski, Univ. of Utah (United States)

Published in SPIE Proceedings Vol. 2528:
Optical and Photonic Applications of Electroactive and Conducting Polymers
Sze Chang Yang; Prasanna Chandrasekhar, Editor(s)

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