Yung-Liang Tung

Efficient white-light-emitting diodes based on poly(N-vinylcarbazole) doped with blue fluorescent and orange phosphorescent materials

We have fabricated polymer white-light-emitting devices possessing a single emitting layer containing a hole-transporting host polymer, poly(N-vinylcarbazole), and an electron-transporting auxiliary, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, doped with a blue-light-emitting amino-substituted distyrylarylene fluorescent dye and an orange-light-emitting osmium phosphor. The doubly doped device exhibited an intense white emission having Commission Internationale de l’Eclairage coordinates of (0.33, 0.34), a high external quantum efficiency of 6.12% (13.2cd∕A), and a maximum brightness of 11306cd∕m2. The color coordinates remained unchanged over a range of operating voltages, even at luminance as high as 1×104cd∕m2.

Organic light-emitting diodes based on charge-neutral Os(II) emitters: generation of saturated red emission with very high external quantum efficiency

The OLED device using 6% of Os(fptz)2(PPh2Me)2 as the dopant emitter in a CBP host and BPAPF as hole transporting material shows an external quantum efficiency of 15.3% and luminous efficiency of 21.3 cd A−1, power efficiency of 6.3 lm W−1 at 20 mA cm−2. An even higher external quantum efficiency of ∼20% was achieved at a low current density of ∼1 mA cm−2.

Synthesis and characterization of fluorinated β-ketoiminate and imino-alcoholate Pd complexes: precursors for palladium chemical vapor deposition

The design and synthesis of Pd complexes with two β-ketoiminate or with two imino-alcoholate chelate ligands is reported. In order to establish their structures in the solid-state, methoxyethyl substituted complexes 1c and 2c were characterized by single crystal X-ray diffraction, showing a square-planar local coordination for the Pd atom, but the β-ketoiminate ligands of 1c gave a bent basal plane involving two chelating hexagons, which was in sharp contrast to the boat configuration of the imino-alcoholate ligands observed in the second complex 2c. Chemical vapor deposition (CVD) experiments were conducted at deposition temperatures of 250–350 °C. Scanning electron micrographs (SEM) were taken to reveal the surface morphologies and grain sizes of the Pd metal thin films. The resulting thin films were found to contain a low level of carbon and oxygen impurities using O2 as the carrier gas, as measured by X-ray photoelectron spectroscopy (XPS).

Phosphorescence of red Os(fptz)(2)(PPh2Me)(2) doped organic light-emitting devices with n and p hosts

We have applied a stericly-hindered red phosphorescent dopant Os(fptz)2(PPh2Me)2 [fptz=3-trifluoromethyl-5-(2-pyridyl)-1,2,4-triazole, PPh2Me=phosphine ligand] in p-type 4,4′-N,N′-dicarbazole-biphenyl or n-type bis(2-methyl-8-quinolinolato)(p-phenylphenolato) aluminum host and found that the latter produced higher luminance efficiency at lower doping concentration. We present a model to rationalize this phenomenon in which the n-type host impedes hole transport, which leads to narrower recombination zone near the hole transport layer/emission layer interface than the p-type host, hence, more effective recombination.