High thermal stability 3, 6-fluorene-carbazole-dendrimers as host materials for efficient solution-processed blue phosphorescent devices

A novel series of solution-processable 3,6-disubstituted-fluorene-carbazole based host materials 36FCzG1 and 36FCzG2 are designed and synthesized. Owing to the highly asymmetry tetrahedral configuration, these hosts exhibit high glass transition temperatures (Tg) (161 and 162 °C, respectively), high triplet energy levels (2.80 and 2.80 eV, respectively), excellent film forming capabilities, and chemical miscibility. Phosphorescent organic lighting-emitting diodes (OLEDs), which base on these host materials doped with the guests of iridium(III) bis(4,6-difluorophenylpyridinato)-picolinate (FIrpic) by spin coating, possesses a low turn-on voltage of 4.0 V, a maximum efficiency of 18.5 cd/A (8.1 lm/W), and a maximum external quantum efficiency of 10.3%. These results show that the devices are among the excellent solution processable blue phosphorescent OLEDs based on dendrimers. Furthermore, a novel way is developed to construct solution processable small molecules based on 3,6-disubstituted fluorene and carbazole dendrimers combined in a highly rigid configuration.