Green phosphorescent iridium dendrimers containing dendronized benzoimidazole-based ligands for OLEDs

Abstract

A series of novel non-conjugated functionalized benzoimidazole-based dendrimers containing peripheral benzyl ether type dendrons have been synthesized and characterized. These compounds undergo cyclometalation with iridium trichloride to form iridium(III) complexes. The emission wavelengths of these dendrimers are in the range from 510 to 530 nm, and the photoluminescence quantum yields (PLQYs) in the range from 0.45 to 0.80. Dendrimers (Gn)(2)Ir(acac) and (Gn)(3)Ir exhibit a reversible one-electron oxidation wave at similar to 0.55 V and similar to 0.37 V (vs. Ag/AgNO3), respectively. With a device configuration of indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid)/4, 4'-bis(N-carbarzolyl)biphenyl:(G2)(3)Ir 20 wt% dopant/1,3,5-tris(2-N-phenyl-benzoimidazolyl)benzene/LiF/Al has a maximum external quantum efficiency (EQE) of 17.6% and a maximum current efficiency of 61.5 cd/A. (C) 2008 Elsevier B.V. All rights reserved.