Synthesis and characterization of solution-processable highly branched iridium (III) complex cored dendrimer based on tetraphenylsilane dendron for host-free green phosphorescent organic light emitting diodes

Solution processable highly branched iridium(III) complex fac-tris(2-phenylpyridyl)iridium-cored dendrimer based on tetraphenylsilane dendron and 2-ethylhexyloxy surface groups was prepared. The structure of dendrimer was confirmed by nuclear magnetic resonance, mass and infrared studies. Thermogravimetric analysis and differential scanning calorimetry studies show the thermal stability (∆T5%) of 625 K with high glass transition temperature of 423 K. Photoluminescence studies of dendrimer showed the core emission at 516 nm in solution and at 521 nm in film, indicating the highly branched non-conjugated tetrahedral tetraphenylsilane dendrons around the core highly inhibit the intermolecular interactions between the cores in the film. The solution processed green emitting phosphorescent organic light emitting diodes based on dendrimer were fabricated and characterized. The device using host free dendrimer as emitter showed the external quantum efficiency of 0.4%. The results show the potential of this new type of dendritic emitting structure in highly efficient solution processed host-free green phosphorescent organic light emitting diodes.