Deep-Red/Near-Infrared Delayed Fluorescence Luminophores Based on Dipyrido[3,2-a:2",3"-c]Phenazine-11,12-Dicarbonitrile for High-Performance OLEDs

Deep-red (DR) and near-infrared (NIR) organic light-emitting diodes (OLEDs) based on purely organic materials hold great potential in various frontier applications, but purely organic DR/NIR materials are far from satisfactory. Herein, a series of tailor-made delayed fluorescence luminophores comprised of electron-withdrawing dipyrido[3,2-a:2 '',3 ''-c]phenazine-11,12-dicarbonitrile and various electron-donating triarylamines are developed, and their thermal and electrochemical stabilities, electronic structures, photophysical properties and electroluminescence (EL) performances are investigated. They exhibit strong NIR emissions (758-767 nm) in neat films and DR/NIR emissions (680-691 nm) with good photoluminescence quantum yields (48-60%) in doped films, and prefer ordered horizontal alignment with high horizontal dipole ratios of 82-90%, which are attributed to the hybrid transition components of excited states, extended molecular plane and intramolecular hydrogen-bonding. Their non-doped OLEDs emit purely NIR light peaking at 820-834 nm with maximum external quantum efficiencies (eta(ext,max)s) of 0.66-1.06%, and thier doped OLEDs radiate DR/NIR emissions peaking at 656-748 nm with superb eta(ext,max)s of 14.4-31.0%. They present even better EL performances in sensitized OLEDs, with DR emissions peaking at 648-656 nm and higher eta(ext,max)s of 29.7-32.9%. These state-of-the-art EL performances demonstrate the great potential of the developed DR/NIR delayed fluorescence luminophores in practical application.