Molecular design of host materials for stable blue phosphorescent organic light-emitting diodes

Stable host materials based on dibenzothiophene and 9-phenylcarbazole were synthesized to elongate the life span of blue phosphorescent organic light-emitting diodes (PHOLEDs). Three host materials with the 9-phenylcarbazole moiety directly linked with dibenzothiophene moiety via 1, 3, and 4- positions of 9-phenylcarbazole were compared in terms of lifetime and efficiency of the blue PHOLEDs. The connection between dibenzothiophene and 9-phenylcarbazole through 3- position of carbazole was an effective way of improving the lifetime of the blue PHOLEDs more than twice and the molecular structure was well correlated with the lifetime of the blue PHOLEDs.