Control of charge transport in iridium(III) complex-cored carbazole dendrimers by generation and structural modification

Abstract

Here, the charge transporting properties of a family of highly phosphorescent iridium(III) complex-cored carbazole dendrimers designed to have improved charge transport by incorporating carbazole units into the dendrons are studied. Firstly, the effect of the dendrimer generation and the role of dendron for materials with one dendron per ligand of the core are considered. It is shown, in contrast to previously reported light-emitting dendrimers, that in this case the carbazolyl-based dendrons have an active role in charge transport. Next, the effect on the charge transport of attaching two dendrons per ligand to the dendrimer core is explored. In this latter case, for the so called "double dendron" material a highly non-dispersive charge transport behavior is observed, together with a time-of-flight mobility of the order of 10-3cm2V-1s-1. Furthermore the lowest energetic disorder parameter (σ) ever reported for a solution-processed conjugated organic material is found, σ < 20 meV. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.