• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1529-1530
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• 2007

The manganese co-doped $Ca_8Mg_1(SiO_4)_4Cl_2:Eu^{2+}$,$Mn^{2+}$ phosphor was synthesized by solid-state reaction and its photoluminescence characteristics were investigated. The synthesized phosphor show two emission spetrums: green band of 512nm and yellow band of 550nm. White light-emitting diodes (LEDs) were fabricated through combination of a 405nm-emitting InGaN chip and a synthesis phosphor in a single package. Under 20mA current, its CIE chromaticity coordinates are x=0.40 and y=0.45 and a color temperature of 4053K.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.591-593
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• 2008

In this report, cerium doped lutetium aluminate ($Lu_3Al_5O_{12}$:Ce) phosphor has been synthesized by the solid state method under reduction atmosphere with mixture gas. The prepared phosphor shows a main luminescent peak at 555nm. Consequently, this phosphor is possible to be applicable to white LED lamp by InGaN chips.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.424-425
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• 2006

Zinc sulfide is a well-known host material of phosphor emitting different radiations dependent on different doping impurities of metallic ion. It emits green, blue, orange-yellow or white colors by doping with activators such as copper, silver, manganese and so on. In this study, manganese, copper and chlorine doped ZnS phosphor (ZnS:Mn,Cu,Cl) was synthesized by solid-state reaction method. The optical properties were investigated according to different concentrations of sulfur and activators used during the synthesis process.

• Journal of the Optical Society of Korea
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• v.16 no.4
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• pp.449-456
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• 2012

For two well-known modulation methods, stepwise current modulation (SCM) and pulse width modulation (PWM), the effects of driving current modulation conditions on chromaticity were experimentally investigated in a white LED lighting system. For the experimental implementation of both SCM and PWM, a white LED lighting was fabricated using phosphor converted (PC) white light emitting diodes (LEDs) and a driving circuit module was developed. By using them, the variations of illuminance, color coordinates, and spectrum were evaluated under various forward current conditions. Through the analysis in color coordinates, yellow shift in SCM and blue shift in PWM were observed on chromaticity diagrams with increasing average driving current. In addition, in order to analyze color deviation quantitatively, color distance before and after current increase, and the correlated color temperature (CCT) were calculated. As a result, for the white LED lighting in both modulation conditions, the maximum difference in the calculated CCT was obtained close to 1000 K. It means that careful consideration is required to be taken in the design of illumination systems to avoid serious problems such industrial accidents.

• Journal of the Semiconductor & Display Technology
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• v.16 no.2
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• pp.44-48
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• 2017

We explain optical and electrical properties of top and bottom-emission structured alternating-current powder electroluminescent devices (ACPELDs) with Ga-doped ZnO(GZO) transparent electrode. The top-emission ACPELDs were layered as the metal electrode/dielectric layer/emission layer/top transparent electrode and the bottom-emission ACPELDs were structured as the bottom transparent electrode/emission layer/dielectric layer/metal electrode. The yellow-emitting ZnS:Mn, Cu phosphor and the barium titanate dielectric layers were layered through the screen printing method. The GZO transparent electrode was deposited by the sputtering, its sheet resistivity is $275{\Omega}/{\Box}$. The transparency at the yellow EL peak was 98 % for GZO. Regardless of EL structures, EL spectra of ACPELDs were exponentially increased with increasing voltages and they were linearly increased with increasing frequencies. It suggests that the EL mechanism was attributed to the impact ionization by charges injected from the interface between emitting phosphor layer and the transparent electrode. The top-emission structure obtained higher EL intensity than the bottom-structure. In addition, charge densities for sinusoidal applied voltages were measured through Sawyer-Tower method.

• Proceedings of the Materials Research Society of Korea Conference
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• 1999.11a
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• pp.177-177
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• 1999

• 한국전기화학회:학술대회논문집
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• 1998.10a
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• pp.65-65
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• 1998

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.295-298
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• 2011

ZnS:Mn, Dy yellow phosphors for White Light Emitting Diode were synthesized by a solid state reaction method using ZnS, $MnSO_4{\cdot}5H_2O$, S and $DyCl_3{\cdot}6H_2O$ powders as starting materials. The mixed powder was sintered at $1000^{\circ}C$ for 4 h in an air atmosphere. The photoluminescence of the ZnS:Mn, Dy phosphors showed spectra extending from 480 to 700 nm, peaking at 580 nm. The photoluminescence of 580 nm in the ZnS:Mn, Dy phosphors was associated with $^4T_1{\rightarrow}^6A_1$ transition of $Mn^{2+}$ ions. The highest photoluminescence intensity of the ZnS:Mn, Dy phosphors under 450 nm excitation was observed at 4 mol% Dy doping. The enhanced photoluminescence intensity of the ZnS:Mn, Dy phosphors was explained by energy transfer from $Dy^{3+}$ to $Mn^{2+}$. The CIE coordinate of the 4 mol% Dy doped ZnS:Mn, Dy was X = 0.5221, Y = 0.4763. The optimum mixing conditions for White Light Emitting Diode was obtained at the ratio of epoxy : yellow phosphor = 1:2 form CIE coordinate.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.4
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• pp.195-200
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• 2013

Novel Sr-Y-Si-Oxynitride yellow phosphors were synthesized and the effect of calcination temperature, reduction temperature and $Eu^{2+}$ concentration on their luminescence properties were studied. Optimal temperature conditions were found to be $1400^{\circ}C$ and $1300^{\circ}C$ for solid-state reaction and reduction, respectively. The synthesized $Ba_9Y_{2+y}Si_6O_{24-3y}N_{3y}:Eu^{2+}$ phosphors showed a single intense broadband emission in the range of 571~587 nm for 450 nm excitation light source. The highest luminescence intensity was obtained with Eu concentration of 3 mol% and concentration quenching was observed beyond 5 mol%. FE-SEM and PSA showed that the synthesized phosphors consists of particles with an average size of ${\sim}8.2{\mu}m$.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.3
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• pp.59-68
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• 2023

Currently, yellow phosphor of Y3Al5O12:Ce3+ (YAG:Ce) fluorescent material is applied to a 450~480nm blue LED light source to implement a white LED device and it has a simple structure, can obtain sufficient luminance, and is economical. However, in this method, in terms of spectrum analysis, it is difficult to mass-produce white LEDs having the same color coordinates due to color separation cause by the wide wavelength gap between blue and yellow band. There is a disadvantage that it is difficult to control optical properties such as color stability and color rendering. In addition, this method does not emit purple light in the range of 380 to 420nm, so it is white without purple color that can not implement the spectrum of the entire visible light spectrum as like sunlight. Because of this, it is difficult to implement a color rendering index(CRI) of 90 or higher, and natural light characteristics such as sunlight can not be expected. For this, need for a method of implementing sunlight with one LED by using a method of combining phosphors with one light source, rather than a method of combining red, blue, and yellow LEDs. Using this method, the characteristics of an artificial sunlight LED device with a spectrum similar to that of sunlight were demonstrated by implementing LED devices of various color temperatures with high color rendering by injecting phosphors into a 405nm deep blue LED light source. In order to find the spectrum closest to sunlight, different combinations of phosphors were repeatedly fabricated and tested. In addition, reliability and mass productivity were verified through temperature and humidity tests and ink penetration tests.