Photoresponse and electroresponse of polymer light-emitting diodes

Z. Valy Vardeny; Xing Wei; Stefan A. Jeglinski

doi:10.1117/12.219551

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15 September 1995 Photoresponse and electroresponse of polymer light-emitting diodes

Z. Valy Vardeny, Xing Wei, Stefan A. Jeglinski

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Proceedings Volume 2528, Optical and Photonic Applications of Electroactive and Conducting Polymers; (1995) https://doi.org/10.1117/12.219551
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

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 (I_EL-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.

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Z. Valy Vardeny, Xing Wei, and Stefan A. Jeglinski "Photoresponse and electroresponse of polymer light-emitting diodes", Proc. SPIE 2528, Optical and Photonic Applications of Electroactive and Conducting Polymers, (15 September 1995); https://doi.org/10.1117/12.219551

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