CN‐Modified Imidazopyridine as a New Electron Accepting Unit of Thermally Activated Delayed Fluorescent Emitters.

Two efficient thermally activated delayed fluorescent (TADF) emitters were developed by utilizing CN‐modified imidazopyridine as an acceptor unit. The CN‐modified imidazopyridine acceptor was combined with either an acridine donor or a phenoxazine donor through a phenyl linker to produce two TADF emitters, Ac‐CNImPy and PXZ‐CNImPy. The acridine‐based Ac‐CNImPy emitter exhibited sky‐blue emission with a CIE coordinate of (0.18, 0.38), whereas the phenoxazine‐donor‐based PXZ‐CNImPy showed greenish‐yellow emission with a CIE coordinate of (0.32, 0.58). A high photoluminescence quantum yield of 80 % was observed for the PXZ‐CNImPy emitter compared with 40 % for the Ac‐CNImPy emitter. Organic light‐emitting diodes based on the PXZ‐CNImPy emitter demonstrated high external quantum efficiency of 17.0 %. Hence, the CN‐modified imidazopyridine unit can be considered as a useful electron acceptor for the future design of highly efficient TADF emitters. [ABSTRACT FROM AUTHOR]