• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.366-369
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• 2001

In this study, the matrix Organic Electroluminescence (OEL) device, that was consisted of R,G,B pixels. We fabricated OEL devices by side by side methode and, used organic material Alq3 as green, DCM as red and Butyl PBD as blue ETL. We investigated the characteristic of brightness and current density for matrix OEL device. As the results, each color devices has minimum about $100cd/m^{2}$ brightness and maximum luminescence was $2500cd/m^2$ in green OEL device.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.235-238
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• 2009

BaMg$Al_{10}O_{17}$ (BAM) co-doped with $Eu^{2+}$ and $Mn^{2+}$ was synthesized in a solid-state reaction and their luminescence properties were investigated as functions of the concentrations of the sensitizer and activator. BAM:$Eu^{2+}$ had a broad blue emission band at 450 nm and BAM:$Mn^{2+}$ exhibited green emission at 514 nm. The energy transfer from $Eu^{2+}$ to $Mn^{2+}$ was mainly of the resonance-type via an electric dipole-quadrupole interaction. Additionally, the addition of various fluxes such as $AlF_3$ and $BaF_2$ in the synthesis improves the moist and thermal stability. This is particularly important for the phosphor in white light emitting diodes (LEDs).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.1
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• pp.75-78
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• 2002

Si thin films on p-type (100) Si substrate have been prepared by a pulsed laser deposition technique using a Nd:YAG laser. The pressure of the environmental gas during deposition was 1 Torr. After deposition, Si thin film has been annealed again at 400-840$^{\circ}C$ in nitrogen ambient. Strong blue photoluminescence (PL) have been observed at room temperature. We report the PL properties of Si thin films with the variation of the annealing temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.366-369
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• 2001

In this study, the matrix Organic Electroluminescence (OEL) device, that was consisted of R,G,B pixels. We fabricated OEL devices by side by side methode and, used organic material Alq3 as green, DCM as red and Butyl PBD as blue ETL. We investigated the characteristic of brightness and current density for matrix OEL device. As the results, each color devices has minimum about 100 cd/㎡ brightness and maximum luminescence was 2500cd/㎡ in green OEL device

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.286.1-286.1
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• 2013

Nowadays, the glare towards the light-emitting diode (LED) lighting source has much attention due to its eco-friendly nature, reduced energy consumption, and low CO2 emission. LEDs can show versatile colors by changing the composition ratio of semiconductors. Phosphors re-emit light by absorbing light from LED, which is the key factor for emission. The endeavor to make replica of natural white light is increasing day by day. Industrially, blue LED chip crowned with a yellow phosphor coated lens gives low quality white light. Newly, many researchers are introducing modern approaches, adding red phosphor to the yellow phosphor to increase the quality of white light. Here, we synthesized structurally and chemically stable europium doped oxyapatite Ca8Gd2(PO4)6O2 nano-crystalline structures by a hydrothermal method. The ultrafine structures were formed due to the effect of ethylenediaminetetraacetic acid, which is confirmed by the transmission electron microscope images. The structural properties were analyzed using the X-ray diffraction patterns.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4291-4295
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• 2010

This paper presents a LED lighting decoration system with a LED candle color control that can independently change its color. The proposed processing was applied to the control of a LED candle that is composed of red, green, blue(RGB) LEDs. In order to go our of use switching device, we developed the LED candle drived luminescence and we will comercialize the result.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.35-39
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• 2005

Phosphor powders of zinc gal late added with Mg and rare-earth elements were prepared by sol id state reaction to improve luminescent properties. Green emitting $ZnMnGa_{2}O_{4}$ reached maximum intensity at Mn=0,005 mole$\%$ and further improvement was achieved by addition of $Mg^{2+}$. Tm, Mg-added zinc gallate phosphor exhibited a strong blue band emission, peaking at about 420 nm with the maximum intensity at the concentration of 0.003 mole$\%$ Mg and 0.015 mole$\%$ Tm. Deepening of the potential wells of the ground and excited states was suggested to be the cause for the enhancement in emission intensity at optimal doping of Mg and Tm.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.280.1-280.1
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• 2016

Generally InGaN/GaN green light emitting diode (LED) exhibits the low quantum efficiency (QE) due to the large lattice mismatch between InGaN and GaN. The QE of InGaN-based multiple quantum wells (MQWs) is drastically decreased when an emission wavelength shifts from blue to green wavelength, so called "green gap". The "green gap" has been explained by quantum confined Stark effect (QCSE) caused by a large lattice mismatch. In order to improve the QE of green LED, undoped graded short-period InGaN/GaN superlattice (GSL) and Si-doped GSL (SiGSL) structures below the 5-period InGaN/GaN MQWs were grown on the patterned sapphire substrates. The luminescence properties of InGaN/GaN green LEDs have been investigated by using photoluminescence (PL) and time-resolved PL (TRPL) measurements. The PL intensity of SiGSL sample measured at 10 K shows stronger about 1.3 times compared to that of undoped GSL sample, and the PL peak wavelength at 10 K appears at 532 and 525 nm for SiGSL and undoped GSL, respectively. Furthermore, the PL decay of SiGSL measured at 10 K becomes faster than that of undoped GSL. The faster decay for SiGSL is attributed to the increased wavefunction overlap between electron and hole due to the screening of piezoelectric field by doped carriers. These PL and TRPL results indicate that the QE of InGaN/GaN green LED with GSL structure can be improved by Si-doping.

• Korean Journal of Materials Research
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• v.25 no.9
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• pp.475-479
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• 2015

$YNbO_4:Yb^{3+}/Er^{3+}$ is synthesized using a solid-state reaction process with a LiCl flux. The effects of the Er/(Yb+Er) ratios ($R_{Er}$) on the up-conversion (UC) and down-conversion (DC) spectra are investigated. The XRD data confirm that the $Yb^{3+}$ and $Er^{3+}$ ions are fully substituted for the $Y^{3+}$ sites. The UC emission spectra activated by 980 nm consists of green and red emission bands, which originate from the $Er^{3+}$ ions through an energy transfer (ET) process from $Yb^{3+}$ to $Er^{3+}$. The UC emission intensity depends on the $R_{Er}$ value, and the findings demonstrate that $R_{Er}{\leq}0.14$ is suitable for an effective UC process. The DC emission spectra under 269 nm radiation of the synthesized powders exhibits not only a strong blue emission assigned to the $[NbO_4]^{3-}$ niobates, but also green peaks that originate from the $Er^{3+}$ ions through an ET process between $[NbO_4]^{3-}$ and $Er^{3+}$.

• Korean Journal of Optics and Photonics
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• v.25 no.4
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• pp.216-220
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• 2014

We have synthesized a $CaMgSi_2O_6:Eu^{2+}$ blue phosphor via a solid-state reaction method. The $CaMgSi_2O_6:Eu^{2+}$ phosphor has monoclinic structure with a space group of C2/c (15), and an emission band peaking at 450 nm (blue) due to the $4f^7-4f^65d$ transition of the $Eu^{2+}ion$. The emission intensity at $100^{\circ}C$ is 54% of the value at room temperature. A white LED was fabricated by integrating a UV LED (400 nm) with our blue phosphor plus two commercial green and red phosphors. The white LED shows a color temperature of 3500 K with a color rendering index of 87 (x = 0.3936, y = 0.3605), and a luminous efficiency of 18 lm/W. The white LED shows a luminance maintenance of 97% after operation at 350 mA for 400 hours at $85^{\circ}C$.