• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.533-536
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• 2008

The anthracene derivatives were synthesized by Suzuki coupling reaction. The thermal, optical and electronic properties of MNAn and BIPAn were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry(DSC), UV-vis absorption, photoluminescen ce spectroscopies, and cyclic voltammetry. The materials exhibit high thermal stability and high per formance in EL devices.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.39-42
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• 2006

A $Eu^{2+}$ doped $BaAl_2S_4$ phosphor was synthesized from BaS, EuS, Al and S powder by vacuum heat treatment. The synthesized powder at $850^{\circ}C$ was composed of only $BaAl_2S_4$ phase. The photoluminescence of $Eu^{2+}$ doped $BaAl_2S_4$ phosphor showed the blue emission centered at 470nm and CIE color coordinate at x=0.12, y=0.11.

• Journal of Information Display
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• v.13 no.1
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• pp.37-42
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• 2012

An empirical functional form was suggested for the analysis of the emission spectrum of high-power light-emitting diode (LED) consisting of a sharp blue peak from the LED chips and a broad yellow peak from the phosphor layer. The peak positions, half widths, shape parameters, and amplitudes of these two peaks were reliably obtained as a function of the temperature, and the results were discussed qualitatively in relation with the junction temperature. The adoption of an inert liquid was found to have significantly reduced the LED temperature and the color shift of the emitted light. The phenomenological approach used in this study may be helpful in the simulation of the LED spectrum under various thermal conditions, and may thus be helpful in the improvement of the device performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.1
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• pp.7-11
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• 2011

Sapphire substrate was patterned by a selective chemical wet etching technique, and GaN/InGaN structures were grown on this substrate by MOVPE (Metal Organic Vapor Phase Epitaxy). The surface of grown GaN on patterned sapphire substrate (PSS) has good morphology and uniformity. The patterned sapphire substrate LED showed better light output than conventional LED that improvement 50%. We think these results come from enhancement of internal quantum efficiency by decrease of threading dislocation and increase of light extraction efficiency. Also these LED showed more uniform emission distribution in angle than conventional LED.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.78.2-78.2
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• 2017

Post-starburst (E+A) galaxies are thought to be in the green valley transition phase between star-forming blue galaxies and quiescent red galaxies. They are identified by their unusual spectra characterized by strong Balmer absorption lines and weak emission lines, indicating a period of starburst followed by abrupt quenching. However, the underlying mechanism that drives the formation of E+A galaxies still remains contradictory or inconclusive. Thus, in order to differentiate between the different formation scenarios of E+A galaxies, we perform a statistical analysis of the environments of E+A galaxies. We spectroscopically identify a large sample of post-starburst galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) using a selection criteria based on $H{\delta}$ equivalent width. We report our findings and discuss their implications in the context of post-starburst galaxy formation.

• Rubber Technology
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• v.13 no.1
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• pp.1-9
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• 2012

Click chemistry had enjoyed a wealthy decade after it was introduced by K.B.Sharpless and his co-worker on 2001. Since there is no optimized method for synthesis of click polymer, therefore, this paper introduced three click reaction methods such as catalyst, non-catalyst and azide-end capping for fluorene-based functional click polymers. The obtained polymers have reasonable molecular weight with narrow PDI. The polymers are thermally stable and almost emitted blue light emission. The synthesized fluorene-based functional click polymers were characterized to compare the effect of click reaction methods on polymer electro-optical properties as well as device performance on quasi-solid-state dye sensitized solar cells (DSSCs) applications. The DSSCs with configuration of $SnO_2:F/TiO_2/N719$ dye/quasi-solid-state electrolyte/Pt devices were fabricated using these click polymers as a solid-state electrolyte components. Among the devices, the catalyzed click polymer composed device exhibited a high power conversion efficiency of 4.62% under AM 1.5G illumination ($100mW/cm^2$).These click polymers are promising materials in device application and $Cu^I$-catalyst 1, 3-dipolar cycloaddition click reaction is an efficient synthetic methodology.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.28.1-28.1
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• 2010

Recent surveys have shown that many early-type galaxies have signatures of ongoing or recent star formation (RSF). These RSF galaxies show blue integrated UV-optical colours that set them aside in the NUV integrated colour-magnitude relation. Among them, NGC 4150 has been observed using the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope to inspect the galaxy with higher spatial resolution. In the WFC3 data, the galaxy reveals ubiquitous near-UV emission and remarkable dusty substructure. Our analysis shows this galaxy to lie in the near-UV green valley, and its pixel-by-pixel photometry exhibits a narrow range of UV-optical colours that are similar to those of nearby E+A (post-starburst) galaxies, and lie between those of M83 (an actively star-forming spiral) and the local quiescent early-type galaxy population. This work reaffirms our hypothesis that minor mergers play a significant role in the evolution of early-type galaxies at late epochs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.252-256
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• 2009

We have developed low driving voltage white organic light emitting diode with a new electron transport material, triphenylphosphine oxide ($Ph_{3}PO$). The white light emission was realized with a rubrene yellow dopant and blue-emitting DPVBi layer. The new electron transport layer results in a very high current density at low voltage, resulting in a reduction of driving voltage. The device with a new electron transport layer shows a brightness of $1150\;cd/m^2$ at a low driving voltage of 4.3 V.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.322.2-322.2
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• 2014

Lighting emitting diodes of n-ZnO/MQW/p-GaN structure are fabricated and investigated. To realize this LED structure, n-ZnO/MQW/p-GaN are grown by MOCVD. At several bias voltages, blue-green light is emitted from the ZnO mesa edge. However, the emission is restricted near the mesa edge. It is seen that the hole current does not spread well. It is because conductivity of p-GaN is extremely small. The break down voltage of the device is small compared to conventional InGaN/GaN LEDs. It is seen that ZnO columnar grain boundaries act as leakage current paths and non-radiative recombination center.

• Journal of the Korean Applied Science and Technology
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• v.22 no.4
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• pp.299-305
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• 2005

In this study, we designed color of tunable and high efficient organic materials using the quantum dynamics and the semi-empirical calculation, and applied this results to the fabrication of organic light-emitting diodes. Also we optimized the molecular structure of phosphorescent materials and the energy transfer from a host to a dye which makes organic light-emitting diodes improve. Using quantum dynamics method, the molecular structures of ligand only and the whole metal chelate were optimized, and these energy levels were calculated. From this test results, we could understand the emission mechanism of phosphors with various ligands as well as design the proper ligands reducing the T-T annihilation and the carrier lifetime. We also could design ligands with various colors using this test method.