Molecular engineering with triptycene groups endows homoleptic Ir(iii) complexes with enhanced electroluminescence properties

Abstract

Emitters with suppressed intermolecular interactions are desired for high efficiency OLEDs. Herein, five phosphorescent homoleptic Ir(III) complexes with a triptycene skeleton were successfully synthesized. Benefitting from the unique rigid and bulky triptycene skeleton, these complexes exhibit excellent thermal and photophysical properties. Their crystal structures indicated that the π–π stacking interactions can be completely eliminated by reasonable combination of the triptycene skeleton and steric hindrance groups. These complexes show significantly good to excellent quantum yields (73.7%–88.9%) and thermal stability (T_d = 364–451 °C). A highly efficient OLED with an external quantum efficiency of up to 27.5% is developed with very low efficiency roll-off and is the most efficient OLED based on phthalazine iridium complexes.