55‐2: <i>Invited Paper:</i> Delocalizing Electron Distribution in Organic Molecules Towards High‐Efficiency, Long‐Lifetime Delayed Fluorescence

Here, we develop TADF emitters with delocalized electron distribution through a secondary acceptor, not only thermodynamically improving the intrinsic molecular stability in both excited and anionic states, but also dynamically fastening the reverse intersystem crossing process for a fast exciton consumption. The targeted compounds as emitters in OLEDs exhibited high maximum external quantum efficiencies of 27.9‐37.1% and remarkably long LT95s (times decay to 95% of the initial luminance) of 380 and 648 h for blue and greenish devices at 1,000 cd/m 2 .