C1-, C2-, and C3-Modified Carbazole Derivatives as Promising Host Materials for Phosphorescent Organic Light-Emitting Diodes.

Herein we unveiled the synthetic approach to C1-, C2-, and C3-modified carbazoles for the first time and designed high-triplet-energy bipolar host materials for green phosphorescent organic light-emitting devices. The compounds revealed excellent performance with a maximum external quantum efficiency as high as 23.6% and extremely low-efficiency roll-off of 2.1% at high brightness of 1000 cd/m2.