Photoresponse and electroresponse of polymer light-emitting diodes

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

doi:10.1117/12.219551

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

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

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.

Citation Download Citation

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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