Synthesis of new bipolar host materials based on 1,2,4-oxadiazole for blue phosphorescent OLEDs

•Novel 1,2,4-oxadiazole based host materials were facile synthesized and used in organic light-emitting diodes.•Their thermal stabilities and optical energy levels revealed that they were suitable for good host materials.•High triplet energies were achieved.•Good blue phosphorescence were obtained.

Two novel bipolar host materials, namely 3,5-bis(4-(9H-carbazol-9-yl)phenyl)-1,2,4-oxadiazole (pCzmOXD) and 3,5-bis(3-(9H-carbazol-9-yl)phenyl)-1,2,4-oxadiazole (mCzmOXD) were designed and synthesized, by incorporating a new block 1,2,4-oxadiazole as the n-type moiety and changing its linking pattern with carbazole. As expected, high triplet energy (over 2.81 eV) for mCzmOXD was achieved due to the intrinsic meta-linkage of 1,2,4-oxadiazole. When both materials were applied in blue phosphorescent organic light-emitting diodes, good performance of 13.0 cd A−1/16.0 cd A−1 were achieved for pCzmOXD and mCzmOXD in iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C′2]bis[(4,6-difluorophenyl)pyridinato-N,C2′] picolinate (FIrpic)-based devices, respectively.

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