• 한국전기전자재료학회논문지
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• 제23권9호
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• pp.701-707
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• 2010

We have synthesized new pure blue-emitting hyperbranched polyfluorene (Hyper-PDHF) through $A_2$ and $B_3$ type monomers via Suzuki coupling polymerization. The weight-average molecular weights ($M_w$) of the Hyper-PDHF was found about 35,000 with polydispersity index as 6.1. The UV absorption peak of the Hyper-PDHF film was at around 335 nm which was far blue shifted than that of linear PDHF film which was found at 380 nm. The pure blue photoluminescene (PL) peak of the Hyper-PDHF was measured at 419 nm as main emission with 397 and 444 nm as shoulder peaks. The Hyper-PDHF showed also higher PL quantum efficiency in solution than linear PDHF (Hyper-PDHF, $\Phi$sol =0.81; PDHF, $\Phi$sol=0.78). The annealed PDHF film (5 hrs on hot plate at $80^{\circ}C$) showed increased shoulder peak emissions and emission color was changed into the green emission. But, Hyper-PDHF film shows almost no excimer emission peak even the film was annealed. The enhanced PL efficiency and no excimer emission of Hyper-PDHF results from the inhibition of excimer formation by the introduction of the hyperbranched system into the polyfluorene backbone.

• 한국전기전자재료학회논문지
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• 제22권9호
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• pp.781-785
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• 2009

We have fabricated simple triple-layer blue-emitting phosphorescent organic light emitting diodes (OLEDs) using different thicknesses (25 and 55 nm) of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) electron transport layers. 1,1-bis[4-bis (4-methylphenyl)- aminophenyllcyclohexane (TAPC), bis[(4,6-di-fluorophenyl)-pyridinate-$N,C^{2'}$]picolinate (FIrpic) and N,N' -dicarbazolyl-3,5-benzene (mCP) were used as hole transport, blue guest and host materials, respectively. The driving voltage, electroluminescence (EL) efficiency and emission characteristics of devices were investigated. The maximum EL efficiency was 20 cd/A in the device with 55 nm BCP layer, which efficiency was about 33% higher than the device with 25 nm BCP layer. The higher efficiency in the 55 nm BCP device resulted from the enhanced electron-hole balance. In the EL spectrum of blue phosphorescent OLED with BCP layer, the relative intensity between 470 and 500 nm peaks was related to the location of emission zone.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.411-412
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• 2007

EL (electro luminescent) is generally studied as a large size plane light emitting device and flexible light source because of it's simple manufacturing process. In this experiment, we manufactured flexible white emitting light source using Ni-foil with blue phosphor and color change materials. With increasing the thickness of color change material, the luminance of white emission is increased and the color coordinate of white color was shifted to pure white of (0.317,0.328) by strong emission of color change materials excited by blue excitation spectra. Also the luminance level was 30% higher in white emitting light device than blue only light source.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.31-32
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• 2008

The structure of OLEDs with conventional heterostructure consists of anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode. NPB used as a hole transport layer and DPVBi used as a blue light emitting layer were graded-mixed at selected ratio. Interface at heterojunction between the hole transport layer and the elecrtron transport layer restricts device's stability. Mixing of the hole transport layerand the emitting layer removes abrupt interface between the hole transport. layer and the electron transport layer. The stability of OLED with graded mixed-layer developed in this study was improved.

• 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.

• 공업화학
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• 제25권3호
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• pp.233-236
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• 2014

유기발광 다이오드(Organic light emitting diodes)는 차세대 평판디스플레이로 학문적으로나 산업적으로 많은 관심을 받고 있다. 그러나 고성능 유기발광 다이오드의 생산을 위해서는 극복해야 할 많은 과제들이 여전히 남아있다. 그중 청색발광물질은 자체의 넓은 밴드갭으로 인해 녹색과 적색 발광재료에 비해 낮은 효율을 보이고 있다. 그러므로 많은 사람들이 높은 효율을 가진 청색 발광물질을 개발하기 위해 많은 노력을 기울이고 있다. 따라서 본 논문에서는 유기발광 다이오드의 기본개념과 청색 발광물질의 개발에 대해 간략하게 소개하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.36-37
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• 2009

We have studied the effect of the hole transporting layers on the device efficiencies blue phosphorescent organic light emitting diodes (PHOLED) with of iridiumIIIbis4,6-di-fluorophenyl-pyridinato-N,C2picolinate (FIrpic) doped 3,5--N,N-dicarbazole-benzene (mCP) host. The highest efficiency of blue PHOLED is strongy dependent on the hole transporting materials, exhibiting the maximum current efficiency.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.52-54
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• 2008

The authors investigated the InGaN/GaN multi-quantum well blue light emitting diodes with the implements of the photonic crystals fabricated at the top surface of p-GaN layer or the bottom interface of n-GaN layer. The top photonic crystals result in the lattice-dependent photoluminescence spectra for the blue light emitting diodes, which have a wavelength of 450nm. However, the bottom photonic crystal shows a big shift of the photoluminescence peak from 444 nm to 504 nm and played as a role of quality enhancement for the crystal growth of GaN thin film. The micro-Raman spectroscopy shows the improved epitaxial quality of GaN thin film.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.545-548
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• 2008

We report the synthesis of blue emitting materials with a new core structure containing indenopyrazine. Non-doped device using one of these materials as a blue emitter was found to exhibit high external quantumn efficiency of 4.6% and excellent color purity of (0.154, 0.078) as well as narrow emission band of 47nm FWHM.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.798-802
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• 2009

New blue emitting materials of o,p-TP-EPY and m,m-TP-EPY were synthesized using two terphenyl units with different structures in the new core of indenopyrazine. EL spectrum of o,p-TP-EPY was more blue shifted than m,m-TP-EPY, and external quantum efficiency of o,p-TP-EPY was showed improvement of about 60% compared to efficiency of m,m-TP-EPY.