Performance and Lifetime of Alq(3)-Based Organic Light-Emitting Diodes Under the Application of Alternating Voltages

Abstract

In order to improve the performance and lifetime of organic light-emitting diodes (OLEDs), several types of alternating-current (AC) voltages were applied to the devices. Optimized condition for the operation of OLEDs was tried to find. The device was manufactured in a structure of ITO/TPD/Alq(3)/LiF/Al. It was found that it is more appropriate to apply square-wave AC voltage rather than the sinusoidal one in operating the OLEDs. Frequency-dependent electroluminescence of the device shows that there is a relatively constant intensity of the luminance below 1 kHz and it is gradually lowered with increasing frequency in a range of frequency from 10 Hz to 100 kHz. Variation of duty ratio of the AC signal applied to the device shows that the electroluminescent (EL) intensity increases as the duty ratio of the AC signal increases. The optimized EL intensity was obtained at around 500 Hz.