CN substituted indolocarbazole as a core structure of exciton harvesting and lifetime extending host for green thermally activated delayed fluorescent emitter

An electron deficient building block, indolo[3,2,1-jk]carbazole-2-carbonitrile (ICCN), was introduced as an electron transport unit of a bipolar host for green thermally activated delayed fluorescent emitter. The electron deficient ICCN effectively functioned as the electron transport unit of the bipolar host and carbazole modified ICCN host achieved high external quantum efficiency of 17.1%. Moreover, the ICCN derived host extended the lifetime of the thermally activated delayed fluorescent device by more than four times.