Effect of dendron generation on properties of self-host heteroleptic green light-emitting iridium dendrimers

A series of self-host heteroleptic green light-emitting iridium (Ir) dendrimers G1 and G2 have been synthesized under mild conditions with high yields, and their photophysical, electrochemical and electroluminescent properties are investigated in detail. Compared with the model compound G0, both G1 and G2 exhibit similar photophysical and electrochemical properties, indicating that the incorporation of carbazole dendrons via a flexible non-conjugated spacer can retain the independence of the emissive Ir core. However, the device performance gradually increases with the increasing dendron generation due to the reduced intermolecular interactions. As a result, a peak luminous efficiency of 17.2 cd/A has been obtained for the G2-based non-doped device, which is about 6 times that of G0. Further dispersing the dendrimer G2 into a host matrix, the efficiency can be improved to 29.2 cd/A. (C) 2012 Elsevier B.V. All rights reserved.