Carbazole-based Multiple Resonance Dendrimers with Narrowband Blue Emission for Solution-Processed OLEDs

Three carbazole-based multiple resonance dendrimers namely D1-BNN, D2-BNN and D3-BNN, are developed for solution-processed narrowband blue organic light-emitting diodes(OLEDs) by introducing the first-, second-, and third-generation carbazole dendrons in periphery of boron, nitrogen-doped polycyclic aromatic hydrocarbon skeleton. Different from D1-BNN containing first-generation carbazole dendron showing moderate photoluminescent quantum efficiency(PLQY) of 68% in solid state and broadened emission bands with full-width at half maximum(FWHM) increasing from 26 nm to 34 nm upon doping concentration growing from 10 wt% to 40 wt%, D3-BNN with the third-generation carbazole dendron exhibits high PLQY of 92% and weak dependence of photoluminescent spectra on doping concentration, which can remain narrowband emissions with unchanged FWHM of 24 nm at same doping concentration range. Solution-processed OLEDs employing D3-BNN as emitter reveal blue electroluminescence at 477 nm with FWHM of 24 nm, and maximum external quantum efficiency(EQE) of 17.3%which is kept at 14.4% at doping concentration of 40 wt%, much superior than the D1-BNN devices showing maximum EQE of 13.0% that drops to 3.7% at 40 wt% doping concentration.