Hole transporting properties of tris(8-hydroxyquinoline) aluminum (Alq3)

Abstract

The hole transporting properties of tris (8-hydroxyquinoline) aluminum (Alq3) were investigated by time-of-flight (TOF) technique between 278 and 373K, and under an applied field range of 0.6–1.3MV∕cm. At room temperature, the hole mobility has a value between 10−9 and 10−8cm2V−1s−1. The hole mobility is at least two orders of magnitude less than electron under identical preparation and measurement conditions. Generally, all hole TOF transients of Alq3 exhibit a nondispersive behavior, with a clear plateau region and a dispersion tail. Two disorder transport models, namely, the Gaussian disorder model (GDM) and the correlated disorder model (CDM), were applied to analyze the temperature and field dependent hole mobility data. The GDM, however, is found to be invalid because it fails to produce a meaningful positional disorder parameter. The CDM gives a better fit to the data, yet the model is still not satisfactory.