Abstract/Summary

We have investigated current–voltage (I–V) characteristics of unipolar and bipolar organic diodes that use phosphorescent dendrimers as the emissive organic layer. Through simulation of the measured I–V characteristics we were able to determine the device parameters for each device structure studied, leading to a better understanding of injection and transport behaviour in these devices. It was found that the common practice of assuming injection barriers are equal to the difference between bare electrode work functions and molecular orbital levels is unsuitable for the devices considered here, particularly for gold contacts. The studies confirm that different aromatic units in the dendrons can give significant differences in the charge transporting properties of the dendrimers.