Benzonitirile modified N type host for exciplex host to enhance efficiency and lifetime in blue phosphorescent organic light-emitting diodes

[Display omitted] •Benzonitrile modified electron transport type host for blue phosphors.•Electron transport type host with deep energy level for exciplex formation.•Efficiency and lifetime improvement by more than 30% using an exciplex host with high triplet energy. Benzonitirile modified host materials, 3-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(triphenylsilyl)benzonitrile (CNmSi-Trz), 3-(4-(dibenzo[b,d]furan-2-yl)-6-phenyl-1,3,5-triazin-2-yl)-5-(triphenylsilyl)benzonitrile (CNmSi-2DBF-Trz) and 3-(4-(dibenzo[b,d]furan-4-yl)-6-phenyl-1,3,5-triazin-2-yl)-5-(triphenylsilyl)benzonitrile (CNmSi-4DBF-Trz), were synthesized for improved efficiency and lifetime in blue phosphorescent organic light-emitting diodes (PhOLEDs). Triazine and benzonitrile units were introduced commonly to the three host materials for electron transporting properties. The three hosts were applied to mixed host as electron transport type hosts with a hole transport type 3,3-di(9H-carbazol-9-yl)biphenyl (mCBP) for blue PhOLEDs. They formed exciplex with mCBP, and the exciplex of CNmSi-2DBF-Trz with mCBP showed high triplet energy above 2.9 eV. As a result, the blue PhOLEDs fabricated with the CNmSi-2DBF-Trz host achieved high EQE over 23% and 650 h lifetime up to 70% of initial luminance at 200 cd/m2 using the exciplex host system with mCBP.