Ir(III) Metal Emitters with Cyano-Modified Imidazo[4,5-b]pyridin-2-ylidene Chelates for Deep-Blue Organic Light-Emitting Diodes

Abstract

Ir(III) carbene complexes have been explored as one of the best blue phosphors for their high performance. Herein, the authors designed and synthesized a series of blue-emitting Ir(III) phosphors (f-ct9a-c), featuring fac-coordinated cyano-imidazo[4,5-b]pyridin-2-ylidene cyclometalates. These Ir(III) complexes exhibit true-blue emission with a peak maximum spanning 448-467 nm, with high photoluminescence quantum yields of 81-88% recorded in degassed toluene. Moreover, OLED devices bearing phosphors f-ct9a and f-ct9b deliver maximum external quantum efficiencies (EQE_max) of 25.9% and 30.3%, together with Commission Internationale de L'Eclairage (CIE_x,y) coordinates of (0.157, 0.225) and (0.142, 0.169), respectively. Remarkably, the f-ct9b-based device displays an incredible EQE of 29.0% at 5000 cd·m^-2. The hyper-OLED device based on f-ct9b and ν-DABNA exhibits an EQE_max of 34.7% and CIE_x,y coordinates of (0.122, 0.131), affirming high potentials in achieving efficient blue electroluminescence.

Keywords: blue; carbene; cyclometalates; iridium; organic light‐emitting diodes.