• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1381-1382
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• 2005

We report improved efficiency in blue electrophosphorescent organic light emitting diodes by introducing an interfacial exciton blocking layer between light emitting layer (EML) and hole transport layer (HTL). Iridium(III) bis [(4,6-di-fluorophenyl)- pyridinato -N,C2']picolinate (FIrpic) was used as blue phosphorescent dopant and JHK6-3 with carbazole and electron transporting group as host and also as the interfacial layer, resulting in drastic increase in quantum efficiency.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.1047-1052
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• 2003

Controlling carrier transport in light emitting polymers is extremely important for their efficient use in organic opto-electronic devices [1]. Here we show that the interactions between single wall carbon nanotubes (SWNTs) and conjugated polymers can be used to modify the overall mobility of charge carriers within nanotube-polymer nanocomposites. By using a unique, double emitting-organic light emitting diodes (DE-OLEDs) structure. we have characterized the hole transport within electroluminescent nanocomposites (nanotubes in poly (m-phenylene vinylene-co-2,5-dioctoxy-p-phenylene) or PmPV). We have shown using this idea that single devices with color tunability can be fabricated. It is seen that SWNTs in PmPV are responsible for hole trapping, leading to shifts in the emission wavelengths. Our results could lead to improved organic optical amplifiers, semiconducting devices, and displays.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 디스플레이 광소자분야
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• pp.119-122
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• 2003

We report a dramatic increase in the photo-stability of a blue-emitting polymer, poly(9,9-dioctylfluorene), achieved by the addition of gold nanoparticles to the polymer. The optical absorption band of gold nanoparticles is tuned to resonate the triplet exciton-ground state band gap energy of the polymer. The photo-oxidation rate of poly(9,9-dioctylfluorene) was drastically reduced by doping the polymer with a very small amount ($10^{-6}-10^{-5}$ volume fraction) of gold nanoparticles. The gold nanoparticles used herein act as the quenching agent of the triplet states and can be directly applied to various blue light emitting polymer thin film ( < 100 nm ) devices.

• Journal of Information Display
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• 제11권2호
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• pp.52-56
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• 2010

High-efficiency organic light-emitting diodes (OLEDs) based on multilayer transparent electrodes (MTEs) are reported. The dielectric/metal/dielectric (DMD) multilayer electrode based on a thin silver layer achieved high sheet conductance as small as $6{\Omega}/sp$ and a tuning capability in the optical and electrical properties by engineering the inner and outer dielectric layers. In the conventional normal bottom-emitting structure, a DMD-based OLED can be fabricated with 90% higher forward luminous efficiency and 30% higher external quantum efficiency (EQE) compared to ITO-based devices. Special attention was paid to the optimization method of such MTE structure considering both the injection and optical structures.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.188-191
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• 2009

A high efficiency deep blue phosphorescent organic light-emitting diode (PHOLED) was developed using a new wide triplet bandgap host material (PPO1) with a phenylcarbazole and a phosphine oxide unit. The wide triplet bandgap host material was synthesized by a phosphornation reaction of 2-bromo-Nphenylcarbazole with chlorodiphenylphosphine. A deep blue emitting phosphorescent dopant, tris((3,5-difluoro-4-cyanophenyl)pyridine)iridium (FCNIr), was doped into the PPO1 host and a high quantum efficiency of 17.1 % and a current efficiency of 19.5 cd/A with a color coordinate of (0.14,0.15) were achieved in the blue PHOLED. The quantum efficiency of the deep blue PHOLED was better than any other quantum efficiency value reported up to now.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1303-1304
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• 2009

In order to apply to the White light emitting diodes (WLEDs), The $Y_2SiO_5:Eu^{3+}$ as red phosphor was synthesized by solid state reaction method. The highest emission of $Y_2SiO_5:Eu^{3+}$ was shown when the $Eu^{3+}$ concentration was 0.02. A single phase was observed from X-ray diffraction (XRD) analysis of synthesized samples and secondary phase wasn't found.

• 한국산학기술학회논문지
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• 제12권10호
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• pp.4590-4599
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• 2011

컬러 시프트 현상은 다양한 색상을 생성하는 유기발광다이오드 소자에 있어서 발광 색상의 순도를 저하시키는 주요 원인으로 작용되어지고 있다. 본 연구에 적용한 유기발광다이오드 소자의 기본 구조는 ITO/${\alpha}$-NPD/$Alq_3$:DCJTB [wt%]/$Alq_3$/Mg:Ag로 구성되어지며, 컬러 시프트가 일어나는 메커니즘을 규명하기 위하여 유기발광다이오드 소자 내에서의 전기광학적인 특성 요인들을 수치 해석하였다. 또한 DCJTB[wt%]의 도핑 농도 비율을 변화시켜 가면서 컬러 시프트의 원인을 조사하였다. 그 결과, 발광층과 정공 수송층의 경계면에서 발생되어지는 호스트에 트랩된 전자들과 자유 정공들 그리고 게스트에 트랩된 정공들과 자유 전자들에 의한 재결합율의 변화가 컬러 시프트 현상의 주요 요인들 중의 하나임을 확인하였다.

• Journal of Information Display
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• 제13권4호
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• pp.151-157
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• 2012

A simple method of fabricating out-coupling structures was demonstrated via solution-processing to enhance light extraction from organic light-emitting diodes (OLEDs). Scattering layers were easily obtained by spin-coating an $SiO_2$ sol solution that contained $TiO_2$ particles. By introducing the scattering layer and the solution-processible corrugated structure as internal and external extraction layers, the OLEDs showed increased external quantum efficiency without a change in the electroluminescence spectrum compared to conventional devices. Using these solution-processible out-coupling structures, nearly all-solution-processed OLEDs with enhanced light extraction could be fabricated. The light extraction enhancement is attributed to the suppression by the out-coupling structures of the light-trapping that arose at the interface of the glass substrate and the air.

• The Journal of Advanced Prosthodontics
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• 제4권2호
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• pp.93-96
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• 2012

PURPOSE. The objective of this study was to compare the light transmittance of zirconia in different thicknesses using various light curing units. MATERIALS AND METHODS. A total of 21 disc-shaped zirconia specimens (5 mm in diameter) in different thicknesses (0.3, 0.5 and 0.8 mm) were prepared. The light transmittance of the specimens under three different light-curing units (quartz tungsten halogen, light-emitting diodes and plasma arc) was compared by using a hand-held radiometer. Statistical significance was determined using two-way ANOVA (${\alpha}$=.05). RESULTS. ANOVA revealed that thickness of zirconia and light curing unit had significant effects on light transmittance ($P$ <.001). CONCLUSION. Greater thickness of zirconia results in lower light transmittance. Light-emitting diodes light-curing units might be considered as effective as Plasma arc light-curing units or more effective than Quartz-tungsten-halogen light-curing units for polymerization of the resin-based materials.

• Journal of Information Display
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• 제3권1호
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• pp.1-5
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• 2002

A series of fully conjugated polymers containing new arylenevinylene units were synthesized and their light-emitting properties were investigated. A bisphosphonate containing tetraphenyl group was made to react with three different dialdehyde monomers to produce fully conjugated alternating copolymers. The photoluminescence (PL) and the electroluminescence (EL) peak wavelengths of the polymers were varied from 500 nm to 460 nm depending on the polymer structure. Single layer EL devices using the polymers as an emissive layer have been fabricated. The single layer EL devices became visible between 12-22 V and emitted blue light.