Effective electroluminescence performance improvement of bis-tridentate iridium complexes by triptycene group modification

To inhibit concentration quenching, three new bis-tridentate iridium complexes modified with triptycene groups were successfully synthesized. The rigid sterically demanding triptycene endows these new complexes with high photoluminescence quantum yields (PLQYs) and low concentration quenching. In air, their PLQYs exceed 0.68 in poly(methyl methacrylate) (PMMA) films and 0.17 in neat powder form, which are significantly higher than that of the reference complex (0.57 and 0.03, respectively). At the same time, the thermal stability of the complex Ir1 is improved and the luminescence wavelength of the complex Ir1 is less affected by the modification of triptycene group. The doped OLED device based on complex Ir1 exhibits excellent electroluminescent efficiencies of 80.1 cd A−1 and 24.0%, which are improved by more than 50% compared with that of reference device. More significantly, the maximum efficiencies of its non-doped device are 17.6 cd A−1, 7.4%, which are improved by more than 300% compared with that of reference device. These results indicate that the triptycene group is very effective functional group to inhibit the concentration quenching of bis-tridentate iridium complexes.