Indolo[3,2,1-jk]carbazole-derived planar electron transport materials realizing high efficiency in green phosphorescent organic light-emitting diodes

Two novel electron transporting materials (ETMs), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)indolo[3,2,1-jk]-carbazole (DPTrz-ICz) and 5,11-bis(4,6-diphenyl-1,3,5-tria-zin-2-yl)-2-phenylindolo[3,2,1-jk]carbazole (2DPTrz-ICz), were developed based on the indolo[3,2,1-jk]carbazole (ICz) core, combined with 2,4-diphenyl-1,3,5-triazine (DPTrz). The introduced ICz core in ETM exhibited enhanced intermolecular charge transport properties owing to its planar and rigid geometry and high triplet energy, demonstrating the potential of designing ETM. Consequently, 2DPTrz-ICz, featuring high triplet energy of 2.84 eV, effectively prevented triplet exciton quenching and showed increased electron mobility owing to the activation of intermolecular hopping charge transfer facilitated by stacking architecture. The two materials were utilized as ETMs in green phosphorescent organic light-emitting diodes. 2DPTrz-ICz exhibited a superior external quantum efficiency of 21.5%, higher than that of the spirobifluorene-derived ETM.