Search

The novel ambipolar hosts of o-CbzBz and o-DiCbzBz contain carbazole and benzimidazole through an ortho-connection. The orthogonal conformations cause the triplet state to be confined at the carbazole units to secure efficient energy transfer. The phosphorescent organic light-emitting diodes (PhOLEDs) show a high current efficiency, power efficiency, and low efficiency roll-off. o-DiCbzBz can be used as a host for sky-blue, green, and orange-red PhOLEDs, giving 57.5, 78.4, and 60.3 cd/A, respectively.

In this report, we demonstrated a series of blue phosphorescent organic light-emitting diodes (OLED) using the mixed host as the partial emitting layer to achieve ultrahigh external quantum efficiency over 30%. The blue phosphorescent emitter was FIrpic and these host materials was developed by Professor Leung in Department of Chemistry, National Taiwan University. By well optimizing the doping ratio among hosts and FIrpic, and designing the device structure to balance carrier in the emitting layer, a ultrahigh efficiency blue OLED could be obtained with external quantum efficiency over 30%.

A new organic host material, PCT comprising pyridine, carbazole and triazole moieties, was doped with a blue emitter bis[2-(4,6"difluorophenyl)pyridinato-C2,N](pico]inato)iridium(III) (FIrpic) to be an emitting layer (EML) of a phosphorescent organic light-emitting diodes device (PhOLED). With various FIrpic concentration (12%, 15% and 18% by volume ratio) in the EML, a series of high efficiency blue PhOLED was demonstrated showing the external quantum efficiency over 20%.