A theoretical design of bipolar host materials for blue phosphorescent OLED.

A series of host molecules have been designed and characterized for use in phosphorescent organic light-emitting diode devices. The parent host molecule was modified by adding nitrogen-containing group at different positions. The first triplet excited (T) and first singlet excited (S) states energies, frontier orbital energy levels, reorganization energies and injection barriers of the molecules designed were calculated in comparison to those of the reference host, emitter, hole and electron transport materials. Interestingly, our results suggest that addition of nitrogen group into the dibenzothiophene by a N-C linkage increases the triplet energy separation and decreases the injection barriers making them suitable for use as blue phosphorescent materials.