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Templated Bipolar Host Materials for Blue Phosphorescent Organic Light-Emitting Devices with Negligible Efficiency
Hong Huang1, Tao Hua1, Nengquan Li1
1Institute of Technology for Future Industry, School of Science and Technology Instrument Application Engineering, Shenzhen University of Information Technology, Shenzhen 518172, China.
Abstract:
Host engineering is one of the most efficient approaches to maximizing the electroluminescent performance of organic light-emitting devices. Herein, two carbazole-based N,N'-Dicarbazolyl-4,4'-biphenyl (CBP) derivatives, (9-(4'-(9H-carbazol-9-yl)-[1,1'-biphenyl]-4-yl)-3-(3-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)-9H-carbazole (CBPmBI), and (9-(4'-(9H-carbazol-9-yl)-[1,1'-biphenyl]-4-yl)-9H-carbazol-3-yl)diphenylphosphine oxide (CBPPO), were designed as bipolar hosts for blue phosphorescent devices. By introducing the electron-withdrawing groups to the backbone of CBP, the bipolar hosts exhibited high triplet energy, enhanced thermal stability, and balanced charge transport. The device constructed with the blue guest emitter bis[2-(4,6-difluorophenyl) pyridinato-C2,N]iridium (III) (FIrpic) showed the excellent electroluminescence performance. For instance, the CBPPO-based devices achieved a maximum current efficiency of 28.0 cd/A, a power efficiency of 25.8 lm/W, and an external quantum efficiency of 14.4%. Notably, the external quantum efficiency retained at14.1% under the brightness of 5000 cd/m2, featuring the negligible efficiency roll-off.
