Synthesis of dibenzothiophene-based host materials and their blue phosphorescent device performances

Two structural isomeric host materials, 9-(4-(dibenzob,d]thiophen-4-yl)phenyl)-9H-pyrido-2,3-b]indole (pDBTCb) and 9-(3-(dibenzob,d]thiophen-4-yl)phenyl)-9H-pyrido-2,3-b]indole (mDBTCb), were designed and synthesized, incorporating dibenzothiophene (DBT) and α-carboline moieties via phenyl linkages and their device performances of phosphorescent organic light-emitting diodes (PHOLEDs) were also investigated. The different linkages between DBT and α-carboline on central phenyl spacer play an important role in the structure–property correlations. Although their photophysical properties were similar regardless of different linkage positions, the bis2-(4,6-difluorophenyl)pyridinato-C²,N](picolinato)iridium(III)-based blue device with mDBTCb, which adopted a meta-linkage showed a significantly higher maximum quantum efficiency of 19.8% as compared to its para-linkage analog, pDBTCb (16.2%). A high quantum efficiency of 19.8% and only ca. 10% reduction of quantum efficiency at 1000 cd/m² were demonstrated from the blue PHOLEDs with the mDBTCb host material.