Suppression of device degradation mechanism by triphenylsilyl group substitution of the host for blue phosphorescent organic light-emitting diodes

The effect of triphenylsilyl group substitution in the host materials for blue phosphorescent organic light-emitting diodes was studied by synthesizing two hole transport type hosts with and without the triphenylsilyl group in the identical backbone structure. The two host materials were applied as the hosts of blue phosphorescent emitter and the comparison of the emission behavior of the two hosts revealed that the triphenylsilyl group suppressed triplet exciton quenching of the blue phosphorescent emitters. As a result, the blue host with the triphenylsilyl group showed improved device efficiency and extended device lifetime in the blue phosphorescent devices. The blue phosphorescent device with the triphenylsilyl group substituted host showed improved external quantum efficiency and elongated device lifetime compared to the triphenylsilyl free host based device. The bulky triphenylsilyl group was effective to extend the device lifetime of the blue phosphorescent device through reduced triplet exciton induced annihilation.