Efficient Deep‐Blue Fluorescent OLEDs Based on a D–π–A Emitter Profiting From Intramolecular Hydrogen Bonds and a Hybridized Excited State

High performance deep-blue emitters with a Commission International de l'Eclairage (CIE) coordinate of CIE_y≤0.08 are highly desired in ultrahigh-definition displays. Herein, we designed and synthesized an efficient D-π-A deep-blue emitter, 2-(6-([1,1' : 3',1''-terphenyl]-5'-yl)pyridin-3-yl)-1-phenyl-1H-phenanthro[9,10-d] imidazole (mPTPH), using the synergistic effect of intramolecular hydrogen bond (H-bond) and hybridized excited state. Single-crystal structure analysis confirmed that there exist intra- and intermolecular H-bond interactions which could inhibit the structure vibration and increase photoluminescence efficiency. The photophysical and theoretical results show that mPTPH exhibited hybridized local and charge-transfer (HLCT) feature with strong deep-blue emission. Ultimately, the non-doped device based on mPTPH exhibited high maximum luminance of 20610 cd m^-2. The doped device achieved high maximum external quantum efficiency of 5.4 % and small efficiency roll-off with deep-blue emission peak of 413 nm and CIE coordinate of (0.16, 0.08).