Jau-Jiun Huang

Orthogonally Substituted Benzimidazole-Carbazole Benzene As Universal Hosts for Phosphorescent Organic Light-Emitting Diodes

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.

Novel Benzimidazole Derivatives as Electron-Transporting Type Host To Achieve Highly Efficient Sky-Blue Phosphorescent Organic Light-Emitting Diode (PHOLED) Device

The development of benzimidazole substituted biphenyls as electron-transporting hosts for bis[2-(4,6-difluorophenyl)pyridinato-C(2),N](picolinato)iridium(III) is reported. Under the optimized conditions, the organic light-emitting diode (OLED) achieves the maximum current efficiency of 57.2 cd/A, power efficiency of 50.4 lm/W, and external quantum efficiency 25.7%.

Networking hole and electron hopping paths by Y-shaped host molecules: promoting blue phosphorescent organic light emitting diodes

1,3,5-(N,N′,N′′)-Tricarbazolyl-2-(benzimidazol-2-yl)benzene (TCbzBz) has been developed as a host for the FIrpic doped blue phosphorescent organic light emitting diodes. The Y-shaped 1,3,5-tricarbazole array networks the host molecules to form continuous hole and electron hopping paths that provide an improved hole mobility of 2.0 × 10−5 cm2 V−1 s−1. Significant breakthroughs on the efficiency of 58.2 cd A−1 and 59.4 lm W−1 with 28% of external quantum efficiency are therefore achieved. Usually aggregation of the emitter molecules will lead to triplet–triplet quenching and significantly hamper the performance of the PhOLEDs. However, the present networked matrix is so spacious that it can accommodate up to 12% of the FIrpic without hampering the device performance. Nano-aggregation in the sublimed film is clearly evidenced by atomic force microscopy, powder X-ray diffractometry, and UV-Vis spectrophotometry.

Modeling of carrier transport in organic light emitting diode with random dopant effects by two-dimensional simulation.

To model the carrier transport in organic light-emitting diodes (OLEDs) with random dopant effects in the emitting layer, two-dimensional simulation was used. By including the Gaussian shape density of states and field-dependent mobility in the Poisson and drift-diffusion solver, the carrier transport, trapping in the dopant state, and radiative recombination were accurately modeled. To examine the model, the current-voltage characteristics of organic light-emitting devices were compared. The host material in the emitting layer was 2,2-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)biphenyl (BImBP), which was doped with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) at various concentrations. By including the random doping model, the trend of mobility was altered and the radiative efficiency fitted experimental values well.

High efficiency blue phosphorescent organic light-emitting diode with partially mixed host

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%.

Blue phosphorescent organic light-emitting diode with triazole host achieving high current efficiency

We demonstrated a blue phosphorescent organic light-emitting diode with the maximum current efficiency and power efficiency of 57.4 cd/A and 51.6 lm/W, respectively, based on trizaole derivatives as the host of the emitting layer.

Novel benzimidazole/carbazole hybrid ambipolar molecules and application in PhOLEDs

The two novel benzimidazole/carbazole hybrid ambipolar molecules, o-CbzDiBz and m-CbzDiBz, were synthesized as hosts for blue PHOLEDs. Bis[2-(4,6-diiluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic)-based devices can achieve 41.86 and 49.31 cd/A of current efficiency in o-CbzDiBz and m-CbzDiBz matrix, respectively.