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

Abstract

AbstractDeep‐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 (ηext,maxs) of 0.66−1.06%, and thier doped OLEDs radiate DR/NIR emissions peaking at 656−748 nm with superb ηext,maxs of 14.4–31.0%. They present even better EL performances in sensitized OLEDs, with DR emissions peaking at 648−656 nm and higher ηext,maxs 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.