Solution‐Processible Red Iridium Dendrimers based on Oligocarbazole Host Dendrons: Synthesis,Properties, and their Applications in Organic Light‐Emitting Diodes

A series of novel red‐emitting iridium dendrimers functionalized with oligocarbazole host dendrons up to the third generation ( red‐G3 ) have been synthesized by a convergent method, and their photophysical, electrochemical, and electroluminescent properties have been investigated. In addition to controlling the intermolecular interactions, oligocarbazole‐based dendrons could also participate in the electrochemical and charge‐transporting process. As a result, highly efficient electrophosphorescent devices can be fabricated by spin‐coating from chlorobenzene solution in different device configurations. The maximum external quantum efficiency (EQE) based on the non‐doped device configuration increases monotonically with increasing dendron generation. An EQE as high as 6.3% was obtained as for the third generation dendrimer red‐G3 , which is about 30 times higher than that of the prototype red‐G0 . Further optimization of the device configuration gave an EQE of 11.8% (13.0 cd A^?1, 7.2 lm W^?1) at 100 cd m^?2 with CIE coordinates of (0.65, 0.35). The state‐of‐the‐art performance indicated the potential of these oligocarbazole‐based red iridium dendrimers as solution processible emissive materials for organic light‐emitting diode applications.