Synthesis and Optoelectronic Properties of Iridium Complex Containing Camphor Based Auxiliary Ligands

Iridium complexes 1 and 2 were synthesized with 2-phenyl quinoline as the main ligand and acetyl acetone, and camphor based pyridyl pyrazole derivatives as the auxiliary ligands. The structures of the complexes were characterized by nuclear magnetic resonance(NMR), infra red(IR) spectrum and mass spectrum(MS). The photophysical and electroluminescent properties of the complexes were also studied. The results show that the luminescence wavelengths of complexes 1 and 2 are 603 nm and 619 nm, respectively, which belong to orange and red light emission accordingly, and the quantum efficiencies are 34% and 53%, respectively, indicating that the camphor based auxiliary ligands could effectively improve the photoluminescence quantum efficiency of iridium complexes. The electroluminescent wavelengths of the complexes 1 and 2 are red-shifted to 612, 622 nm, respectively, indicating that the camphor based auxiliary ligands could effectivelyreduce thered shift of luminescence. The maximum external quantum efficiency of the device based on complex 1 is 0.014%, and the maximum brightness is 30.2 cd/m². Compared with the device based on complex 1, the external quantum efficiency of complex 2 is increased to more than 3 times, the maximum external quantum efficiency reaches 0.044%, and the maximum brightness is 48.6 cd/m². Moreover, its color coordinates are (0.64, 0.35), and close to the standard red color coordinates. Therefore, the introduction of camphor group in the auxiliary ligand can effectively improve the luminescence efficiency of the complexes, and make the luminescence color insensitive to their concentration. These results are useful for the design and development of organic electroluminescent materials with excellent comprehensive performance.