Triphenylamine Dendronized Iridium(III) Complexes: Robust Synthesis, Highly Efficient Nondoped Orange Electrophosphorescence and the Structure–Property Relationship

New triphenylamine dendronized homoleptic Ir(III) complexes, namely Ir-G1, Ir-G2, and Ir-G3, with six, eighteen, and up to forty-two triphenylamine units, respectively, are designed and efficiently synthesized through convergent strategy. Both linear enlargement of the dendritic arms and the “double-dendron” strategy are applied to maximize the degree of site-isolation of the emissive center. The relationship between the dendritic structures and their photophysical, electrochemical, and electrophosphorescent performances is investigated. Phosphorescent organic light-emitting diodes (PhOLEDs) employing the dendrimers as solution-processed emitters are fabricated. The nondoped devices with Ir-G1 and Ir-G2 as emitters display very high efficiencies and small values of efficiency roll-off. For example, a device with Ir-G1 as emitter exhibits the best results ever reported for solution-processed orange phosphorescent devices with maximum luminous efficiency of 40.9 cd A –1 and power efficiency of 39.5 lm W –1 . Moreover, the maximum power efficiency of the nondoped device is nearly three times higher than that of the doped control device by doping Ir-G1 into the general polymer matrix. This indicates that incorporation of triphenylamine moieties into the sphere of iridium(III) core is a simple and effective approach to develop highly efficient host-free dendritic phosphors.