CN-Modified Host Materials for Improved Efficiency and Lifetime in Blue Phosphorescent and Thermally Activated Delayed Fluorescent Organic Light-Emitting Diodes.

CN-modified host materials, 9-(2-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-carbazole-3-carbonitrile (o-CzCN) and 9-(3-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-carbazole-3-carbonitrile (m-CzCN), which can improve the external quantum efficiency and lifetime of both blue phosphorescent and thermally activated delayed fluorescent (TADF) emitters were developed. A molecular design approach to stabilize the molecular structure and reduce the energy gap produced two high triplet energy host materials of o-CzCN and m-CzCN compatible with the phosphorescent and TADF emitters. The new host materials lowered operation voltage, increased quantum efficiency, and elongated lifetime of both phosphorescent and TADF devices.