Optimizing Charge Transfer and Out‐Coupling of A Quasi‐Planar Deep‐Red TADF Emitter: towards Rec.2020 Gamut and External Quantum Efficiency beyond 30 %.

Herein, we report a deep‐red TADF emitter pCNQ–TPA, composed of quinoxaline‐5,8‐dicarbonitrile (pCNQ) acceptor and triphenylamine (TPA) donor. pCNQ–TPA supported its OLED with desired CIE coordinates of (0.69, 0.31) and the record maximum external quantum efficiency of 30.3 %, which is the best red TADF diode with Rec.2020 gamut for UHDTV. It is showed that through tuning pCNQ–TPA doping concentration, intra‐ and inter‐molecular charge transfer are balanced to synchronously improve emission color saturation and TADF radiation, and remedy aggregation‐induced quenching, rendering photoluminescence quantum yield (PLQY) reaching 90 % for deep‐red emission peaked at ≈690 nm. Quasi‐planar structure further endows pCNQ–TPA with an improved horizontal ratio of emitting dipole orientation, which increases light out‐coupling ratio to 0.34 for achieving the state‐of‐the‐art device efficiencies. [ABSTRACT FROM AUTHOR]