Dibenzothiophene derived hosts with CN substituted carbazole for blue thermally activated delayed fluorescent organic light-emitting diodes

•Dibenzothiophene derived host materials with CN substituted carbazole moieties.•Low driving voltage, improved efficiency and extended lifetime in blue thermally activated delayed fluorescent organic light-emitting diodes.•Increased bond dissociation energy under negative polaron by introducing CN substituted carbazole moiety.

In this work, dibenzothiophene type host materials modified with 9H-carbazole, 9H-carbazole-3-carbonitrile and 9-phenylcarbazole were synthesized for high quantum efficiency and elongated lifetime in blue thermally activated delayed fluorescent (TADF) organic light-emitting diodes. Three host materials having one or two CN modified carbazole units were prepared for strengthened chemical bond as well as improved electron transport properties. The host materials designed using the carbazole and CN modified carbazole units built on the dibenzothiophene core showed low driving voltage, high quantum efficiency and elongated lifetime at the same time without any sacrifice of device performances in the blue TADF devices.

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