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.