Electrical properties of organic light-emitting diodes (OLEDs) studied by impedance spectroscopy in ultra-high vacuum

Rudi Ono; Michael Kiy; Ivan Biaggio; Peter Guenter

doi:10.1117/12.416908

2 February 2001 Electrical properties of organic light-emitting diodes (OLEDs) studied by impedance spectroscopy in ultra-high vacuum

Rudi Ono, Michael Kiy, Ivan Biaggio, Peter Guenter

Author Affiliations +

Proceedings Volume 4105, Organic Light-Emitting Materials and Devices IV; (2001) https://doi.org/10.1117/12.416908
Event: International Symposium on Optical Science and Technology, 2000, San Diego, CA, United States

Abstract

Alq₃-based organic light emitting diodes (OLEDs) were prepared by molecular beam deposition in Ultra-High Vacuum (UHV) and their electrical properties were studied by impedance spectroscopy before they were exposed to any impurity gases. To characterize the fundamental injection processes, we studied the simplest OLED structure, consisting of a single layer of Alq₃ between an ITO anode and a Mg cathode. In UHV, and below the threshold voltage for luminescent, instabilities in the frequency dependence of the resistivity, as well as in the current vs. voltage characteristics, are observed, which could be related to inhomogeneous contacting at the electrodes. When the same experiment is performed in air, both kinds of instabilities disappear, which demonstrates that exposure to atmospheric gas plays a role in stabilizing the contact and injection properties in the devices. Additionally, the impedance spectrum in air below the threshold voltage for luminescent shows an additional feature that hints to two different regions in the Alq₃ layer, which we assign to the effect of Mg atoms which diffused into the Alq₃ layer during deposition.

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Rudi Ono, Michael Kiy, Ivan Biaggio, and Peter Guenter "Electrical properties of organic light-emitting diodes (OLEDs) studied by impedance spectroscopy in ultra-high vacuum", Proc. SPIE 4105, Organic Light-Emitting Materials and Devices IV, (2 February 2001); https://doi.org/10.1117/12.416908

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