Hyung-Sun Kim

Synthesis and characterization of new blue light emitting alternating terphenylenevinylene carbazylenevinylene copolymer

A new terphenylenevinylene carbazylenevinylene alternating copolymer with the advantage of poly(p-phenylenevinylene) (PPV), poly(p-phenylene)(PPP) and poly(carbazole) was designed, synthesized and characterized. The polymer structure was confirmed by various spectroscopic analyses and the number average molecular weight (Mn) of the obtained polymer was 7,800. The resulting polymer was thermally stable with high glass transition temperature (Tg) (150°C), and was readily soluble in common organic solvents. Cyclic voltammetry study revealed that the HOMO and LUMO energy levels of the polymer were 5.37 and 2.47 eV, respectively. The ITO/ PEDOT/polymer/Al device fabricated from the polymer emitted bright sky blue light with a maximum peak of around 478 nm. The device showed the maximum brightness of 1,200 nW with a turn-on voltage of 7 V.

Effective Electrophosphorescence Emitting Devices by Using New Type Ir(III) Complex with Bluky Substistuent Spacers

The new green Ir(III) complex, fac-tris[4-methyl-2-(4′-trimethylsilylph-enyl)pyridine] [Ir(msippy)3], is synthesized and phosphorescent light emitting devices fabricated by using them as triplet emissive dopants. Ir(dsippy)3 in UV-Vis. spectra showed absorption band at 395 nm originating from 1MLCT. The EL devices with configuration of ITO/CuPc (10 nm)/α -NPD (40 nm)/CBP-Ir(msippy)3 (20 nm)/BCP (10 nm)/Alq3 (40 nm)/LiF (1 nm)/Al (100 nm).showed the emission maximum at 516 nm, due to the radiative decay from 3MLCT state to ground state. The 6% doped devices showed the maximum efficiency of 49.9 cd/A and power efficiency 25.3 lm/W. The observed PL quantum efficiency (0.43) of the [Ir(msippy)3] in CH2Cl2 shows slightly higher than that of reported Ir(ppy)3 (Φ = 0.40).

Novel blue-light-emitting poly(terphenylenevinylene) derivative

The blue electroluminescent polymer, poly(terphenylenevinylene) derivative which has advantages of poly(p-phenylene) and poly(p-phenylenevinylene), was prepared by the Suzuki coupling reaction. The structure and properties of the polymer, was analyzed by various spectroscopic methods. The obtained polymer has good solubility and thermal stability. The polymer film showed maximum absorption and emission at 340 and 450 nm, respectively. A blue electroluminescence (λ max = 450 nm) was obtained from the light-emitting diode of ITO/PDHPPV/Al-Li with turn on voltage of 8 V.

The Alignment of Liquid Crystals on the Film Surfaces of Soluble Aromatic Polyimides Bearing t-Butylphenyl and Trimethylsilylphenyl Side Groups

With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4′-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4′-trimethylsilylphenyl)pyromellitic dianhydride (BTPD), and 2,2′-bis(4″-tert-butylphenyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyimides, BBPD-ODA, BBPD-MDA, BBPD-FDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4′-oxydianiline (ODA), 4,4′-methylenediamine (MDA), and 4,4′-(hexafluoroisopropylidene) dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from 0.45×10−4 – 1.37×10−4 J/m2 and from 0.86×10−5 – 4.26×10−5 J/m2, respectively, depending on the polyimides. The pretilt angles of the LCs were in the range 0.10–0.62°. In summary, the soluble aromatic polyimides reported here are promising LC alignment layer candidates for the production of advanced LC display devices.

A Novel Phenothiazine Derivative for Application in High Performance Red Emitting Electroluminescent Device

The new red emitting materials based on phenothiazine and DCM were synthesized by Knoevenagel condensation following Vilsmeyer-Haack formulation. The obtained materials showed good thermal stability and amorphous property. The ITO/CuPc/NPB/Alq3:KSR-1 (0.2%)/Alq3/LiF/Al device showed 3.5 cd/A of efficiency and CIE color coordinate of (0.46, 0.47) at 10 mA/cm2 and 29000 cd/m2 of maximum brightness at 11 V and 512 mA/cm2. In the device using the Alq3:KSR-1 (0.5%) as emitting material device, 1.5 cd/A of efficiency and CIE color coordinate of (0.55, 0.42) at 10 mA/cm2 and 19200 cd/m2 of maximum brightness at 12 V and 702 mA/cm2 were observed.

Synthesis and Characteristics of Novel Poly (Terphenylenevinylene) Derivative Containing Benzoxazolyl Group

Poly(1,4-phenylene-2′-methoxy-5′-ethylhexyl-1′,4′-phenylene-1″,4″-phenylene- α -benzoxazolylvinylene) (PTPBOV) was synthesized through the Suzuki reaction of diboronic acid and dibromide and following end-capping reaction. The electron affinity level of the PTPBOV containing benzoxazolyl group was 2.76 eV.

Synthesis and characterization of perylene‐based pyrrolopyrone derivative for organic thin film transistor

Abstract Perylene‐based pyrrolopyrone derivative (PPD) was synthesized via condensation reaction with perylenetetracarboxylic dianhydride and 1,2‐phenylenediamine as n‐type channel material. The structure of PPD was characterized by spectroscopic methods such FT‐IR and 1H‐NMR. PPD exhibited high thermal stability (Td5wt% : 560 °C) and was found to be soluble only in protonic solvents with high acidity such as methane sulfonic acid and trifluoroacetic acid. The PPD solution showed maximum absorption and emission at 601 and 628 nm, respectively. Thin film transistors were fabricated by vacuum deposition and solution casting method. The electron mobilities of the devices were achieved as high as 0.17 x 10–6 cm2/Vs for vacuum deposited device and 0.4 x 10−6 cm2/Vs for spin coated device, respectively.