Frequency-dependent response in ITO/Alq(3)/Al organic light-emitting diodes

Abstract

Frequency-dependent response of organic light-emitting diodes was studied in a device structure of ITO/Alq(3) (60 nm)/Al. Frequency was varied from 40 Hz to 1 MHz and the bias voltage was varied from -5 to +13 V. We have interpreted the frequency dependent response in terms of equivalent circuit model of parallel combination of resistance R-p and capacitance C-p. From the frequency-dependent response, we are able to obtain characteristic crossover frequency omega(0) separating resistive and capacitive response. And we found that there is an effect of interfacial polarization in the frequency range well below the crossover frequency when the applied voltage is lower than turn-on voltage. (C) 2004 Elsevier B.V. All rights reserved.