Sulfone‐Incorporated Multi‐Resonance TADF Emitter for High‐Performance Narrowband Blue OLEDs with EQE of 32

The blue multi‐resonance thermally activated delayed fluorescence materials, simultaneously realizing narrow full‐width at half‐maximum, high external quantum efficiency (EQE), and low efficiency roll‐off, remains a formidable challenge. Herein, three novel emitters, namely PTZBN1, PTZBN2, and PTZBN3, are designed by gradual peripheral modification in boron/nitrogen (B/N) embedded polycyclic skeleton, which exhibit progressively hypsochromic‐shifted emission from 490 nm (PTZBN1) to 468 nm (PTZBN3) with photoluminescence quantum yields up to 98%. In particular, the incorporation of sulfone unit in the boron/nitrogen (B/N) embedded polycyclic skeleton provides a simple but effective tactic for narrowband blue emission. The organic light‐emitting diodes based on PTZBN2 achieve one of the‐state‐of‐the‐art EQEs of 34.8% with electroluminescence (EL) peak at 478 nm. Impressively, PTZBN3‐based device exhibits not only a high maximum EQE of 32.0% with EL peak at 468 nm, but also low efficiency roll‐off. A simple design tactic for narrowband blue emitter is demonstrated by incorporating sulfone unit into the boron/nitrogen (B/N) embedded polycyclic skeleton. The resulting blue organic light‐emitting diodes achieve a high external quantum efficiency of 32.0% and low efficiency roll‐off.