Exciton stabilizing high triplet energy n-type hosts for blue phosphorescent organic light-emitting diodes

An exciton stabilizing electron transport type (n-type) host material was developed for application in long lifetime blue phosphorescent organic light-emitting diodes (PhOLEDs). A conjugation breaking diphenylsilyl backbone structure combined with a diphenyltriazine unit was a basic molecular platform to obtain high triplet energy and electron transport property. Two hosts with and without carbazole were synthesized as the bipolar and unipolar n-type hosts derived from diphenylsilyl backbone and diphenyltriazine unit. The blue PhOLEDs using the two hosts showed high external quantum efficiency above 20% and blue color coordinate of (0.14, 0.17). Particularly, the bipolar n-type host with the carbazole unit extended the device lifetime by more than 1.4 times compared with the unipolar host and by more than three times relative to a conventional diphenyltriazine based host without the diphenylsilyl core because of the exciton stabilizing function of the host. This work proved the potential of the diphenyltriazine and carbazole merged diphenylsilyl skeleton as a chemical platform of the n-type hosts.