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 doubledendron 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 W(-1) W. 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.