Integrating Asymmetric O−B−N Unit in Multi‐Resonance Thermally Activated Delayed Fluorescence Emitters towards High‐Performance Deep‐Blue Organic Light‐Emitting Diodes

Abstract

AbstractDeveloping deep‐blue thermally activated delayed fluorescence (TADF) emitters with both high efficiency and color purity remains a formidable challenge. Here, we proposed a design strategy by integrating asymmetric oxygen‐boron‐nitrogen (O−B−N) multi‐resonance (MR) unit into traditional N−B−N MR molecules to form a rigid and extended O−B−N−B−N MR π‐skeleton. Three deep‐blue MR‐TADF emitters ofOBN,NBNandODBNfeaturing asymmetric O−B−N, symmetric N−B−N and extended O−B−N−B−N MR units were synthesized through the regioselective one‐shot electrophilic C−H borylation at different positions of the same precursor. The proof‐of‐concept emitterODBNexhibited respectable deep‐blue emission with Commission International de l′Eclairage coordinate of (0.16, 0.03), high photoluminescence quantum yield of 93 % and narrow full width at half maximum of 26 nm in toluene. Impressively, the simple trilayer OLED employingODBNas emitter achieved a high external quantum efficiency up to 24.15 % accompanied by a deep blue emission with the corresponding CIE y coordinate below 0.1.