Sung-Hyun Jung

Effects of Complex on Electrical Properties of LB Films Using Dendritic Macromolecules

One of the most peculiar characteristics of dendritic macromolecules is their controlled molecular structure and orientation, which means that they have a practical application in achieving a highly organized molecular arrangement. We attempted to fabricate the G4-48PyP dendrimer Langmuir-Blodgett (LB) films containing 48 pyridinepropanol functional end group that could form a complex structure with metal ions. Also, we have investigated the surface activity at the air-water interface as well as the electrical properties for the monolayers of pure G4-48PyP dendrimer and its complex with Fe 2+ ions. The electrical properties of the ultra-thin dendrimer LB films were investigated by studying the current-voltage characteristics of metal/dendrimer LB films/metal (MIM) structure. The calculated conductivity σ values and barrier height Φ b values of pure G4-48PyP dendrimer and its complexes with Fe 2+ ions are 9.56×10 -16 and 1.46×10 -14 S/cm, 1.18 and 1.10 eV, respectively. As a result, the metal ion around G4-48PyP dendrimer can contribute to the formation of network structure among dendrimers and the change of electrical properties.

Direct synthesis and luminescent properties of new silicon-based alternating copolymers

A new class of silicon-based alternating copolymers having a thiophene or fused thiophene unit was synthesized to be used as electroluminescent materials using the Heck reaction between distyrylsilane monomers and appropriate thiophene dibromides. The incorporation of organosilicon units with the aromatic or aliphatic groups on the silicon atoms into π-conjugated systems improved their processability and interrupted the π-conjugation length. The resulting polymers were highly soluble in common organic solvents. They could be spin-cast onto various substrates to give highly transparent homogeneous thin films. Their glass transition temperatures were in the range of 94 to 116 °C. The UV-visible absorbance spectra of the resulting polymers appear at the wavelength range of 400 to 416 nm, due to the strong delocalization of the π-conjugated thiophene units. The silicon-based alternating copolymers showed a strong PL peak at around 512-526 nm in the green region.

Blue electroluminescence from novel silicon-based copolymers at low operating voltages

Abstract Novel silicon-based copolymers exhibit the ground-state absorption band maxima around 340390 nm and their photoluminescence in blue region. The blue light-emitting diodes (LED) fabricated with the copolymers could be successfully operated at the considerable low voltages compared to those for other blocked PPV copolymers. The introduction of both silicon and carbazole moieties into PPV main chain results in an interesting dependencies of EL spectral feature on the operating voltage for LED. In order to know the origin of the dependence, we have investigated PL and its excitation spectra of the silicon based copolymeric systems.

High Mobility Hole Extraction Material for Organic Solar Cell Application

We report a high mobility hole extraction material, N,N,N′,N′,-tetrakis(biphenyl-4-yl)benzidine (TBBD) for organic solar cell applications. Its highest occupied molecular orbital energy value at 5.3 eV is well matched with a donor layer and its high mobility of 1.74 × 10−2 cm2/Vs brings out an easy and rapid extraction of holes from the donor material. The TBBD incorporated device showed significant improvement of open-circuit voltage, resulting in power conversion efficiency improvement of 9% compared with reference device.

Preparation and properties of the crosslinked phenol-formaldehyde thin films

We fabricated insulating LB films using p-hexadecoxyphenol (p-Hp), which is amphiphilic phenol and can form polyion complexes with formaldehyde at the air-water interface. Also, the possibility for insulation layers of electronic devices was investigated such as conductivity, dielectric constant and activation energy. The conductivity, dielectric constant and activation energy of p-HP LB films are as follows: pure water > 1% formaldehyde subphase > heat-treatment of 1% formaldehyde subphase.

Blue Electrluminescence from Novel Silicon-Based Copolymers at Low Operating Voltages

Abstract Novel silicon-based copolymers show the UV-visible strong absorption bands around 347∼387 nm. Their maximum photoluminescence (PL) wavelengths for silicon-based copolymers appeared around 420∼480 nm in the blue region. The present copolymers with a relatively short π-conjugation length exhibit blue light-emitting diodes (LED) at the low operating voltages, due to the reduction of the LUMO level in luminescent polymers by introducing silicon atoms in luminescent polymers as well as the d-orbital participation of silicon atoms.

P‐13: New 23‐in. Dyna‐Flat CDT

According to our new 23 inch CDTs, screen distortion can be reduced without a concave portion as compared with conventional flat-type CDTs in which the central portion of a panel appears to be inwardly curved. A better impact strength can be achieved by making a shadow mask cylindrical curvature horizontal direction. In order to attain high resolution without a focus difference between left and right side beams, a coma compensator is employed, and a rectangular deflection yoke is employed for saving energy.

Pd-Catalyzed Direct Synthesis of Novel Silicon-Based Copolymers for Tunable Light-Emitting Diodes

Abstract A series of silicon-based copolymers was synthesized by the Pd-catalyzed Heck reaction of the distyrylsilane monomers with various aromatic dibromides. The incorporation of organosilicon units with the flexible alkyl side group into the polymer rigid backbone would afford processable electroluminescent materials and interrupt the regular π-conjugated chains. The resulting polymers were highly soluble in common organic solvents. The UV-Visible absorbance of the present polymers shows strong absorption bands at around 365∼400 nm. Their maximum photoluminescence (PL) wavelength for SiPPV analogues appeared 470 nm in the blue emission region. The single layer light-emitting diode based on the present copolymer emits the blue emissive light at the operating voltage of 9 V.