• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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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.

• Proceedings of the IEEK Conference
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• 2002.06b
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• pp.25-28
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• 2002

We have been fabricated white organic light emitting diode with two-wavelength ard mixing blue emit in DPVBi (4, 4-bis(2, 2-diphenylvinyl)-1, 1 -biphenyl)layer and yellow emit in rubrene (5, 6, 11, 12-tetraphenylnaphthacene)as emitting layer which are controlled with thickness. This device emits white light emitting in CIE (0.29, 0.33), 1000cd/$m^2$ at DC 18V.

• KSBB Journal
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• v.28 no.6
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• pp.428-432
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• 2013

The antimicrobial properties of Light-Emitting Diode (LED) are an area of increasing interest. The aim of this study was to evaluate the bactericidal effects of blue (peak at 456 nm), green (peak at 518 nm), red (peak at 654 nm) and blue-green combined (blue 456 nm : green 558 nm = 69:31) LED irradiation to pathogenic bacteria. For this, LED equipment providing power density of $10mW/cm^2$ was installed and plates were exposed to 0.9 or $3.0mW/cm^2$ to irradiate bacteria with 3.2 to $259.2mW/cm^2$ of energy density. As a result, blue and combined LED have shown bactericidal effects on Escherichia coli KCTC 1467 and Listeria monocytogenes ATCC 19115 after irradiation of $3.0mW/cm^2$ for 2 and 4 hr, respectively. Staphylococcus aureus KCTC 1916 was inhibited at 518 nm green LED irradiation. However, red LED irradiation showed no inhibitory effect to the other tested strains. Light technology that utilizes the bactericidal properties of blue (at 456 nm) and blue-green(blue 456 nm : green 558 nm = 69:31) combined LED may have potential applications in the food industry sector.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.675-679
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• 2004

The existing conjugated blue emitting material polymer which has been used for the two-wavelength method white-emission has good stability and low operating voltage as merits, but the imbalanced carrier transport has been indicated as problem area. We have introduced a novel blue emitting material having perylene moiety unit with hole transporting ability and blue emitting property and triazine moiety unit with electron transporting ability into the same host chain. We have synthesized N-[p-(perylen-3-y1)pheny1]methacry1 amide (PPMA) monomer and [N-(2,4-dipheny1-1,3,5-triazine)pheny1 methacry1 amide] (DTPM) monomer having blue light-emitting unit and electron transport unit, respectively by three steps. A novel non-conjugated blue emitting material Poly[N -[p­(perylene-3-y1) pheny1] methacry1 amide-co-N-[P-(4,6-dipheny1-1,3,5-triazine-2-y1]pheny1]methacry1 amide] (PPPMA-co-DTPM) copolymer having electron transporting unit was synthesized by the solution polymerization of PPMA and DTPM monomers with an AIBN initiator and showed high yield of $75{\%}$. It was very soluble in common organic solvents, and the fabrication of the thin film using a spin coating method was very simple. The PPPMA exhibited a good thermal stability.

• Transactions on Electrical and Electronic Materials
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• v.5 no.5
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• pp.173-179
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• 2004

The influence of heavily Si impurity doping in the GaN barrier of InGaN/GaN multi-quantum well structures of blue light emitting diodes were investigated by growing samples in metal-organic chemical vapor deposition. The delta-doped sample was compared to the sample with the undoped barrier. The delta-doped sample shows the tunneling behavior and forms the energy level of 0.32 eV for tunneling and the photoemission of the 450-nm band. The photo-luminescence shows the blue-shifted broad band of the radiative transition due to the inclusion of Si delta-doped layer indicating that the delta doping effect acts to form the higher energy level than that of quantum well. The dislocation may provide the carrier tunneling channel and plays as a source of acceptor. During the tunneling of hot carrier, there was no light emission.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.481-481
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• 2009

For a new generation of white light sources, we present the first example of a concentration-independent ultimate white-light-emitting molecule based on excited-state intramolecular proton transfer materials. Our molecule is composed of covalently linked blue- and orange-light-emitting moieties between which energy transfer is entirely frustrated, leading to the production of reproducible, stable white photo- and electroluminescence.

• Applied Science and Convergence Technology
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• v.25 no.1
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• pp.1-6
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• 2016

Quantum dots (QDs) are considered as excellent color conversion and self-emitting materials for display and lighting applications. In this article, various technologies which can be used to realize white light emission with QDs are discussed. QDs have good color purity with a narrow emission spectrum and tunable optical properties with size control capabilities. For white light emission with a color-conversion approach, QDs are combined with blue-emitting inorganic and organic light-emitting diodes (LED) to generate white emission with high energy conversion efficiency and a high color rendering index for various display and lighting applications. Various device structures for self-emitting white QD light-emitting diodes (QD-LED) are also reviewed. Various stacking and patterning technologies are discussed in relation to QD-LED devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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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.

• Korean Journal of Materials Research
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• v.25 no.1
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• pp.1-8
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• 2015

This study suggested comprehensive structural characterization methods for the commercial blue light emitting diodes(LEDs). By using the Z-contrast intensity profile of Cs-corrected high-angle annular dark field scanning transmission electron microscope(HAADF-STEM) images from a commercial lateral GaN-based blue light emitting diode, we obtained important structural information on the epilayer structure of the LED, which would have been difficult to obtain by conventional analysis. This method was simple but very powerful to obtain structural and chemical information on epi-structures in a nanometer-scale resolution. One of the examples was that we could determine whether the barrier in the multi-quantum well(MQW) was GaN or InGaN. Plan-view TEM observations were performed from the commercial blue LED to characterize the threading dislocations(TDs) and the related V-pit defects. Each TD observed in the region with the total LED epilayer structure including the MQW showed V-pit defects for almost of TDs independent of the TD types: edge-, screw-, mixed TDs. The total TD density from the region with the total LED epilayer structure including the MQW was about $3.6{\times}10^8cm^{-2}$ with a relative ratio of Edge- : Screw- :Mixed-TD portion as 80%: 7%: 13%. However, in the mesa-etched region without the MQW total TD density was about $2.5{\times}10^8cm^{-2}$ with a relative ratio of Edge- : Screw- :Mixed-TD portion of 86%: 5%: 9 %. The higher TD density in the total LED epilayer structure implied new generation of TDs mostly from the MQW region.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.439-442
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• 2008

A mixed host structure of TCTA and TPBI was used in orange emitting layer and host composition was critical to device performances of PHWOLEDs. PHWOLEDs with TPBI host in orange emitting layer showed high quantum efficiency of 10.3 % at $1000\;cd/m^2$ with little change of CIE coordinates of (0.32, 0.34) from $100\;cd/m^2$ to $10,000\;cd/m^2$.