Deep-Blue Triplet-Triplet Annihilation Organic Light-Emitting Diode (CIE ≈ 0.05) Using Tetraphenylimidazole and Benzonitrile Functionalized Anthracene/Chrysene Emitters.

Herein, new deep-blue triplet-triplet annihilation (TTA) molecules, namely 4-(10-(4-(1,4,5-triphenyl-1H-imidazol-2-yl)phenyl)anthracen-9-yl)benzonitrile (TPIAnCN) and 4-(12-(4-(1,4,5-triphenyl-1H-imidazol-2-yl)phenyl)chrysen-6-yl)benzonitrile (TPIChCN), are designed, synthesized, and investigated as emitters for organic light-emitting diodes (OLED). TPIAnCN and TPIChCN are composed of polyaromatic hydrocarbons of anthracene (An) and chrysene (Ch) as the cores functionalized with tetraphenylimidazole (TPI) and benzonitrile (CN) moieties, respectively. The experimental and theoretical results verify their excellent thermal properties, photophysical properties, as well as electrochemical properties. Particularly, their emissions are in the deep blue region, with TTA emissions being observed in their thin films. By utilization of these molecules as emitters, deep blue TTA OLEDs with CIE coordinates of (0.15, 0.05), high external quantum efficiency of 6.84%, and high exciton utilization efficiency (η) of 48% were fabricated. This result manifests the potential use of chrysene as an alternate building block to formulate new TTA molecules for accomplishing high-performance TTA OLEDs.