Carbazole‐Fused Double Boron Multiple Resonance Pure Fluorescent Emitters for High‐Performance Narrowband Green OLEDs

Abstract This work proposes a strategy of fusing two multiple resonance (MR) units (boron/oxygen) with carbazole as a π‐bridge. This approach successfully yielded three narrowband green pure fluorescent materials, namely, DtBO‐CzP , DtBO‐CzMeP , and DtBO‐CztBuP . TADF‐sensitized OLEDs based on the target compound exhibited high performance, with their FWHM being less than 40 nm, which is lower than that of other traditional fluorescent materials (>50 nm). It is worth noting that the maximum EQE of devices based on DtBO‐CzMeP is 25.2% and the maximum brightness exceeds 90 000 cd m −2 , which is relatively high in green pure fluorescent TSF‐OLEDs. This work not only enriches the diversity of narrowband pure fluorescent materials but also offers a unique strategy for the design of narrowband fused polycyclic aromatic hydrocarbons.