meta-Substituted benzophenones as multifunctional electroactive materials for OLEDs

Abstract meta-Substituted benzophenones bearing tetrahydrocarbazole, phenoxazine and 2,7-ditert-butyl-9,9-dimethylacridine moieties were synthesized as materials exhibiting both thermally activated delayed fluorescence and aggregation induced emission enhancement. The derivatives showed improved HOMO and LUMO separation compared to that of the corresponding derivatives with para-linkage which lead to the minimized singlet-triplet energy gap of ca. 0.04 eV. By employing the acridan-substituted benzophenone derivative as non-doped emissive layer in OLED, a green device with external quantum efficiency of 1.93% was obtained with the CIE coordinates of (0.37, 0.57). More efficient triplet population employment was achieved after doping the acridan-substituted benzophenone derivative with red phosphorescent emitter bis(1-phenyl-isoquinoline)(acetylacetonate)Iridium(III). Red phosphorescent device exhibited small efficiency roll-off and a relatively high external quantum efficiency of 8.6%. External quantum efficiency of 7.60% was achieved for green device based on host:guest system using emitter 10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-10H-phenoxazine which exhibited thermally activated delayed fluorescence.