Solution processable red iridium dendrimers containing oligocarbazole dendrons for efficient nondoped and doped phosphorescent OLEDs

Abstract

Solution processable red Ir dendrimers named R-D1, R-D2 and R-D3, which contain a quinoline-based homoleptic complex as the core and oligocarbazole as the dendron, have been facilely and successfully designed and synthesized via a post-dendronization procedure. With the increasing dendron generation from R-D1 to R-D3, the intermolecular interactions and luminescence quenching in solid states are found to be effectively prevented because of encapsulation from the outer dendrons. As a result, the third-generation dendrimer R-D3 achieves the best nondoped device performance, revealing a promising EQE of 10.5% (9.2 cd A⁻¹, 7.0 lm W⁻¹) with CIE coordinates of (0.67, 0.33). Furthermore, the doped devices of R-D3 show a wide doping concentration window in the range of 5–30 wt%, and a maximum EQE as high as 18.3% (25.7 cd A⁻¹, 33.0 lm W⁻¹) is realized at about a 10 wt% doping content. The results can compete well with vacuum-deposited small molecular red phosphors, representing important progress on solution processable phosphorescent dendrimers with red emission.