• Journal of the Korean Society of Visualization
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• v.10 no.1
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• pp.34-39
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• 2012

In the present study, oxygen transfer process across gas-liquid interface in a Y-shape micro-channel is quantitatively visualized using the micro laser induced fluorescence (${\mu}$-LIF) technique. Diffusion coefficient of Oxygen ($D_L$) is estimated based on the experimental results and compared to its theoretical value. Tris ruthenium (II) chloride hexahydrate was used as the oxygen quenchable fluorescent dye. A light-emitting diode (LED) with wavelength of 450 nm was used as the light source and phosphorescence images of fluorescent dye were captured by a CMOS high speed camera installed on the microscope system. Water having dissolved oxygen (DO) value of 0% and pure oxygen gas were injected into the Y-shaped microchannel by using a double loading syringe pump. In-situ pixel-by-pixel calibration was carried out to obtain Stern-Volmer plots over whole flow field. Instantaneous DO concentration fields were successfully mapped according to Stern-Volmer plots and DL was calculated as $2.0675{\times}10^{-9}\;m^2/s$.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.609-613
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• 2005

Advanced mobile communication devices require a bright, high information content display in a small, light-weight, low power consumption package. In this paper we will outline our progress towards developing such a low power consumption active-matrix flexible OLED ($FOLED^{TM}$) display. Our work in this area is focused on three critical enabling technologies. The first is the development of a high efficiency long-lived phosphorescent OLED ($PHOLED{TM}$) device technology, which has now proven itself to be capable of meeting the low power consumption performance requirements for mobile display applications. Secondly, is the development of flexible active matrix backplanes, and for this our team are employing poly-Si TFTs formed on metal foil substrates as this approach represents an attractive alternative to fabricating poly-Si TFTs on plastic for the realization of first generation flexible active matrix OLED displays. Unlike most plastics, metal foil substrates can withstand a large thermal load and do not require a moisture and oxygen permeation barrier. Thirdly, the key to reliable operation is to ensure that the organic materials are fully encapsulated in a package designed for repetitive flexing. We also present progress in operational lifetime of encapsulated T-PHOLED pixels on planarized metal foil and discuss PHOLED encapsulation strategy.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.183-188
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• 2012

A blue phosphorescent $Ir(dfpypy)_3$ (dfpypy:fluorinated pyridine-pyridine ligand) complex with meridional configuration has been synthesized by newly developed effective method and its solid state structure and photoluminescence are characterized. For this complex, mer-$Ir(dfpypy)_3$, the glass-transition and decomposition temperatures appear at $160^{\circ}C$ and $384^{\circ}C$ respectively in TGA and DSC experiments, which indicates that this complex has high thermal stability. In a crystalline structure, an average Ir-C bond length of mer-$Ir(dfpypy)_3$ is slightly longer than that of fac-$Ir(dfpypy)_3$, which assumed to be due to the weak trans-influence. The absorption and emission spectra are observed more red-shifted in mer-$Ir(dfpypy)_3$ than fac-$Ir(dfpypy)_3$. In addition, the former is readily oxidized than the latter in electrochemical behavior.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.315-319
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• 1999

Properties of both photoluminescence and long-phosphorescent for Eu, Dy-codoped $SrAl_2O_4$ powder phosphor synthesized by solid reaction method were investigated by PL instrument. Two intense peaks in the emission spectrum measured at 10 K are observed near 450 nm (2.755 eV) and 520 nm (2.384 eV) wavelength, but at 300 K the main peak of 520 nm wavelength is presented. After the removal of light excitation (360 nm), the excellent after-glow characteristic of the phosphorescence were obtained as a result of low decay tiem, although the after-glow intensities of phosphor vary exponentially with the times.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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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.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.5
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• pp.188-192
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• 2015

Gemological and spectroscopic properties of HPHT synthetic diamonds from New Diamond Technology (NDT) company in St. Petersburg (Russia) were examined. Their color (colorless, near-colorless with some boron and Fancy blue with high boron content) and clarity ($VVS-SI_1$) grades were comparable to those of top natural diamonds. NDT synthetic diamonds fluoresced and phosphoresced blue or orange under SWUV light. Photoluminescence spectra revealed H3 center with very small intensity and NV centers. The intensity of H3 in NDT synthetic diamond has very weak in comparison with natural one. Using a combination of gemological and spectroscopic tests, gem-quality synthetic diamonds from NDT can be distinguished from natural diamonds of similar quality.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.247-250
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• 2015

Organic light-emitting diode (OLED) research field has received great attention from academic and industrial circles. Recently, The technical feature of OLEDs is more and more attractive in the lighting market, including area emission characteristics different from other existing light sources. Features are environmentally friendly and efficient use of energy, large area, ultra-light weight, and ultrathin shape, etc. Furthermore, OLED light became the mainstream of next-generation lighting to replace the light emitting diode (LED) fluorescent light. This article summarizes phosphorescent emitting materials that have been applied to white OLEDs. In particular, the chemical structures and device performances of the important yellow, orange, and red phosphorescent emitting materials is discussed. Systematic classification and understanding of the phosphorescent materials can aid the development of new light-emitting materials.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.381-388
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• 2015

Organic Light Emitting Diodes (OLEDs) have been receiving great attention in academic and industrial fields, and it is being actively applied to mobile display, as well as large area TV and next-generation flexible display due to their excellent advantages. In addition, the scope of research on OLED materials and device fabrication technology is getting expanded. This review discusses the principle and basic composition of OLED and also classifies OLED materials with different chemical structures according to their usages. Systematic classification of OLEDs by technical concept and material characteristics can help developing new emitting materials.

• Journal of the Korean Ceramic Society
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• v.45 no.8
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• pp.477-481
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• 2008

$Eu^{2+}$ and $Dy^{3+}$ co-doped strontium aluminate, $SrAl_2O_4$ long phosphorescent phoshor was fabricated and its photoluminescence was characterized. The phosphor, $SrAl_2O_4:Eu^{2+},Dy^{3+}$ was synthesized by a coprecipitation in which metal salts of $Sr(NO_3)_2$, $Al(NO_3)_3{\cdot}9H_2O$, were dissolved in $(NH_4)_2CO_3$ solution with adding $Eu(NO_3)_3{\cdot}5H_2O$ and $Dy(NO_3)_3{\cdot}5H_2O$ as a activator and co-activator, respectively. The coprecipitated products were separated from solution, washed, and dried in a vacuum dry oven. The dried powders were then mixed with 3 wt% $B_2O_3$ as a flux and heated at $800{\sim}1400^{\circ}C$ for 3 h under the reducing ambient atmosphere of 95%Ar+$5%H_2$ gases. For the synthesized $SrAl_2O_4:Eu^{2+},Dy^{3+}$, properties of photoluminescence such as emission, excitation and decay time were examined. The emission intensity increased as the annealing temperature increased and showed a maximum peak intensity at 510 nm with a broad band from $400{\sim}650\;nm$. Monitored at 520 nm, the excitation spectrum showed a maximum peak intensity at $315{\sim}320\;nm$ wavelength with a broad band from $200{\sim}500\;nm$ wavelength. The decay time of $SrAl_2O_4:Eu^{2+},Dy^{3+}$ increased as the annealing temperature increased.

• Journal of Photoscience
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• v.10 no.2
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• pp.185-187
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• 2003

The preparation and the photophysics of organometallic Pt(II) and Ir(III) complexes with 6-ch1oro-3-phenylpyridazine (H6Clppdz) are reported. $K_2$PtCl$_4$ and IrCl$_3$ㆍn$H_{2}O$ cleanly cyclometalate with H6Clppdz, forming the corresponding chloro-bridged dimers, (6Clppdz)Pt($\mu$-Cl)$_2$Pt(6Clppdz) and (6Clppdz)$_2$Ir($\mu$-Cl)$_2$Ir(6Clppdz)$_2$ in good yield. These chloro-bridged dimers are cleaved with acetylacetone (Hacac) to give the corresponding monomer, (6Clppdz)Pt(acac) and (6Clppdz)$_2$ Ir(acac), respectively. Both complexes show bright orange luminescence at room temperature and the emission wavelengths are different depending on the metal and the structure of complexes. (6Clppdz)Pt(acac) shows two sharp emission bands in shorter wavelength ($\lambda$$_{em}$=541 and 580 nm), while (6Clppdz)$_2$ Ir(acac) shows a broad emission band in longer wavelength ($\lambda$$_{em}$=615 nm). Strong spinorbit coupling due to the heavy metal atom allows for the formally forbidden mixing of the $^1$MLCT with the $^3$MLCT and $^3$$\pi$-$\pi$$^{*}$ states.