Impedance characteristics of ITO/Alq(3)/Al organic light-emitting diodes depending on temperature

Abstract

Temperature-dependent impedance characteristics of TTO/Alq(3)/Al organic light-emitting diodes were studied in the frequency range from 40 to 108 Hz, and the temperature was varied from 10 to 300 K. At each temperature, the frequency-dependent complex impedance was measured under discrete bias voltages from -6 to +20 V, and the voltage-dependent impedance was measured at 10(2) Hz, 10(3) Hz, 10(4) Hz, and 10(5) Hz. A Cole-Cole plot shows that there is one relaxation, and a parallel capacitor-resistor network in series with a contact resistance could be considered as an equivalent electrical circuit to this device. As the temperature decreases, a radius in the Cole-Cole plot increases, which indicates an increase of resistance of the device. (C) 2006 Elsevier B.V. All rights reserved.