Yoon Soo Han

Synthesis of conjugated polymers containing anthracene moiety and their electro‐optical properties

Both fully conjugated polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene-alt-9,10-anthrylene vinylene] [poly(MEHPV-AV)] and conjugated/nonconjugated block copolymers poly(alkanedioxy-2-methoxy-1,4-phenylene-1,2-ethenylene-9,10-anthrylene-1,2-ehthenylene-3-methoxy-1,4-phenylene)[poly(BFMPx-AV), (x = 4, 8, and 12)] were synthesized by Horner–Emmons reaction utilizing potassium tert-butoxide. Of these synthesized polymers poly(BFMP4-AV) and poly(BFMP8-AV), which has four and six methylene groups as solubility spacer in the main chain exhibited liquid crystalline to isotropic transition in addition to the two first order transitions. Light-emitting diode (LED)s made from the organic solvent soluble poly(BFMP12-AV) as emitting layer showed blue shift in the emission spectrum compared to the one made from fully conjugated poly(MEHPV-AV). Although poly(BFMP12-AV) had higher barrier to the electron injection from cathode than poly(MEHPV-AV), the luminance efficiency of LED made from poly(BFMP12-AV) was about 25 times higher than the one made from poly(MEHPV-AV), which had fully conjugated structure. LEDs fabricated by both poly(BFMP12-AV) and poly(MEHPV-AV) exhibited Stokes shift in the range of 155 to 168 nm from the absorption maximum due to the excimer formation between the ground and excited state anthracene groups.

Electroluminescent Property and Photolithographic Process of Photosensitive Random Copolymers

ABSTRACT A series of poly(N-vinyl carbazole)-based random copolymers containing photosensitive cinnamoyl moieties capable of generating negative type patterned images were synthesized and characterized. First, poly(N-vinyl carbazole-ran-hydroxyethyl methacrylate) copolymers, P(VK-ran-HEMA), were prepared by free radical polymerization of VK and HEMA monomers using AIBN as an initiator in THF. In second step, cinnamoyl groups were introduced by post reaction. Photoluminescent properties of synthesized photosensitive copolymers were measured and, upon UV exposure, negative patterned images with high resolution were produced by standard photolithographic process.

Synthesis of Polyazomethine Type Conjugated Polymers as Light Emitting Materials

Abstract Aromatic dialdehyde based on phenothiazine and aromatic diamine were used to synthesize polyazomethine type conjugated polymer, poly(PZ-PI) which had good solubility in common organic solvents. The UV absorption maximum(λmax,UV) and edge(λedg,UV) of poly(PZ-PI) were observed at 415 and 510 nm, respectively. The threshold voltage of ITO/polymer/Mg and ITO/polymer/Alq3(100 Å)/Mg device was at 10 V and 7 V, respectively. Besides double layer LED with Alq3 exhibited both enhanced emission intensity and efficiency compared to the single layer LED.

Blue Emitting Polymers as Host Materials of Phosphorescent Dopant and Their Electroluminescent Properties

ABSTRACT Two types of blue electroluminescent conjugated polymers, poly(BP-alt-BCV) and poly(BFMP12-BPV), were prepared by Horner-Emmons polycondensation and used as host polymers for the phosphorescent dopant, (bsn)2Ir(acac). Poly(N-vinylcarbazole) (PVK), known as a blue emitting material, was also used for comparison with these polymers. Electrophosphorescence of PLEDs with these dopant/host systems was investigated in terms of luminescence, efficiency, emission color, and energy transfer. The poly(BP-alt-BCV) showed blue emission of high color purity (x = 0.18, y = 0.19), however, poly(BP-alt-BCV) host/phosphorescent (bsn)2Ir(acac) dopant showed red emission (x = 0.60, y = 0.37) due to an efficient energy transfer from poly(BP-alt-BCV) host polymer to phosphorescent (bsn)2Ir(acac) dopant.

Synthesis of conjugated polymers containing biphenyl group and their electro-optical properties

Abstract Two types of conjugated polymer, poly(MEHPV-co-BPV)s and poly (MEHPV-alt-BPV), were synthesized by dehydrohalogenation and Honer-Emmons condensation, respectively. Single layer type light-emitting diodes were fabricated utilizing synthesized polymers and their electro-optical properties were examined. Emission spectrum of poly (MEHPV-co-BPV)s had two peaks in the blue and orange region which originated from BPV and MEHPV moiety, respectively. This may be due to the mixture of two homopolymers or the macroblock nature of the BPV and MEHPV unit in the poly(MEHPV-co-BPV)s. However, LED made from poly(MEHPV-alt-BPV) showed a relatively sharp single peak at the yellow-green region due to the alternating nature of the repeat units.

MOLECULARLY DOPED LIQUID CRYSTALLINE POLYMER AS A HOLE TRANSPORT LAYER IN ORGANIC ELECTROLUMINESCENCE DEVICE

Abstract Organic thin film electroluminescence devices were fabricated by molecularly doped method with N,N′-Diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD) as a hole transport agent, tris(8-quinolinolato) aluminium(III) (Alq3) as an emitting and electron transport agent, and poly(methyl methacrylate) (PMMA), polycarbonate (PC), side chain liquid crystal polymers (SCLCP) and copolymer as matrix for TPD. The effect of polymer matrix and hole transport layer fabrication method on the electroluminescence characteristics were examined. The highest intensity and stability of EL device was obtained by film casting method using dichloroethane as a solvent at a polymer/TPD concentration of 0.005 wt% and evaporation temperature of 30° C. The electroluminescence intensity increased in the order of PMMA>PC>SCLCP as polymer matrix. The luminance started at voltage as low as 3 V and reached the maximum luminance of 756 cd/m2 at 11 V in the EL device consisted of ITO/SCLCP:TPD/Alq3/Mg (SCLCP/TPD=30/7...

Fabrication of Electrophoretic Display Panel Using Prepatterned Barrier Rib

Fabrication process of electrophoretic display panels was investigated by utilizing transparent soft mold press, which enables to guide uniform packing of charged TiO2particles and colored particles for color e-Paper display. For this process, transparent soft mold was prepared by reacting silicone solution(silicone prepolymer/curing agent = 10/1 wt./wt.)into the base mold. While pressed with the transparent soft mold under 1.5 ∼ 3.0 Kgf/cm2of pressure at 60 ∼ 90°C, the photosensitive film was exposed to UV light at 365 nm in the range of 800 ∼ 2,000 mJ/cm2. The transparent soft mold was demolded by rolling up to give electrophoretic display panels with precise geometry. The process of obtaining colored electrophoretic display was also discussed.