Paradigm change of blue emitters: Thermally activated fluorescence emitters as long-living fluorescence emitters by triplet exciton quenching

Deep blue fluorescent organic light-emitting diodes were developed using boron derived 5,9-diphenyl-5H,9H-[1,4]benzazaborino[2,3,4-kl]phenazaborine (DABNA) and 2,12‐di‐tert‐butyl‐5,9‐bis(4‐(tert‐butyl)phenyl)‐5,9‐dihydro‐5,9‐diaza‐13b‐boranaphtho[3,2,1‐de]anthracene (t-DABNA) as fluorescent emitters rather than thermally activated delayed fluorescent emitters for long lifetime. The DABNA and t-DABNA boron emitters were doped in the 9,10-bis(1-naphtyl)anthracene (α-ADN) host to harvest only singlet excitons while quenching triplet excitons for long-term stability. The t-DABNA emitter showed high external quantum efficiency of 7.6% as fluorescent emitters and lifetime longer than that of a conventional pyrene derived blue emitter. This work demonstrated the usefulness of the boron derived emitters as deep blue fluorescent emitters rather than thermally activated delayed fluorescent emitters by overcoming short lifetime drawback through triplet exciton quenching. The paradigm change of the thermally activated delayed fluorescent emitters enabled the development of the deep blue fluorescent organic light-emitting diodes with excellent long-term stability.