Multiple Resonance Dendrimers Containing Boron, Oxygen, Nitrogen-Doped Polycyclic Aromatic Emitters for Narrowband Blue-Emitting Solution-Processed OLEDs.

In contrast to small-molecule multiple resonance emitters processed via vacuum evaporation technology, the design of multiple resonance dendrimers is presented by introducing the first- and second-generation carbazole dendrons in the periphery of boron, oxygen, nitrogen-doped polycyclic aromatic skeleton, for efficient narrowband blue electroluminescence by a solution process. The multiple resonance dendrimers not only keep the narrowband emission of the polycyclic aromatic skeleton, but also can suppress their intermolecular aggregation by steric carbazole dendrons, overcoming the unwanted spectral broadening in the solid state. The resultant first-generation carbazole dendrimer exhibits narrowband blue emission with promising photoluminescent quantum efficiency of 94% and delayed fluorescence with a lifetime of 139.1 µs in the solid-state film. Solution-processed organic light-emitting diodes based on the dendrimers reveal electroluminescence at 488 nm with full-width at half maximum of 39 nm, the maximum luminous efficiency of 29.2 cd A -1 , and maximum external quantum efficiency of 13.4%.