Silicon‐Bridged Cyclic Multi‐Resonance TADF Emitters Enable Enhanced Electrochemical Stability and High Performance in Blue Organic Light‐Emitting Devices

Abstract Boron‐based multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters have attracted considerable attention as a promising approach for achieving high color purity and ≈100% internal quantum efficiency in organic light‐emitting devices (OLEDs). Although many MR‐TADF emitters have been developed to date, achieving high external quantum efficiency (EQE), it remains challenging to simultaneously realize long operational lifetimes, especially in blue OLEDs with CIE y <0.20. In this study, novel blue MR‐TADF emitters named DPSi‐R‐BN derivatives are designed to address this issue. By introducing a cross‐linked structure into the DABNA‐1 skeleton via a silicon bridge and enhancing the bond dissociation energy (BDE) of the fragile carbon–nitrogen bond, the electrochemical stability of the emitters is successfully improved. The resulting blue OLED exhibitsed an EQE of 24.5%, a narrow full width at half maximum of 24 nm, and CIE coordinates of (0.137, 0.175). Most notably, the device shows a 1.4‑fold improvement in operational lifetime (LT 80 = 373/111 h at 500/1000 cd m −2 ) compared to the conventional t‐DABNA ‐based device.