• 한국세라믹학회지
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• 제53권4호
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• pp.381-385
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• 2016

Recently, white LEDs, especially, warm white LEDs have been intensively investigated due to outstanding optical properties, long term stability and low power consumption. In this study, mixed type and patterned type of remote phosphors were prepared by screen printing process employing green and red phosphor. Each type of remote phosphor exhibited distinctive photoluminescence spectrum. For example, the mixed type of remote phosphor exhibited unique spectrum, while the patterned type showed expectable spectrum depending on the concentration of phosphors. This indicates that a small amount of red phosphor dramatically reduced the green photoluminescence in the case of mixed-type remote phosphor, whereas the effect was negligible in the patterned-type remote phosphor. The possibility of undesirable chemical reaction was further investigated by using scanning electron microscopy and X-ray diffraction.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.636-639
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• 2004

We have synthesized a $Eu^{2{\cdot}}$ -activated $Sr_3MgSi_2O_8$ blue phosphor and $Ba^{2{\cdot}}$ co-doped $Sr_2SiO_4$ yellow phosphor investigated an attempt to develop white LEDs by combining it with a GaN blue LED chip. Three distinct emission bands from the GaN-based LED and the ($Sr_3MgSi_2O_8$:Eu + $Ba^{2{\cdot}}$ co-doped $Sr_2SiO_4$:Eu) phosphor are clearly observed at 405nm, 455 nm and at around 540 nm, respectively. These three emission bands combine to give a spectrum that appears white to the naked eye. Our results show that GaN (405 nm chip)-based ($Sr_3MgSi_2O_8$:Eu + $Ba^{2{\cdot}}$ co-doped $Sr_2SiO_4$:Eu) exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1338-1342
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• 2005

We have synthesized an $Eu^{2+}$-activated $Sr_3MgSi_2O_8$ blue phosphor and $Ba_2SiO_4$ green phosphor and $Ba^{2+}$ co-doped $Sr_3SiO_5$ red phosphor investigated an attempt to develop white LEDs by combining it with a GaN blue LED $chip(\lambda_{em}=405 nm)$. Three distinct emission bands from the GaN-based LED and the $(Sr_3MgSi_2O_8:Eu\; +\; Ba_2SiO_4:Eu\; +\; Ba^{2+}\; co-doped\; Sr_3SiO_5:Eu)$ phosphor are clearly observed at 460nm, 520 nm and at around 600 nm, respectively. These three emission bands combine to give a spectrum that appears white to the naked eye. Our results show that GaN (405 nm chip)-based $(Sr_3MgSi_2O_8:Eu\; +\; Ba_2SiO_4:Eu\; +\; Ba^{2+}\; co-doped\; Sr_3SiO_5:Eu) exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce.

• 한국산학기술학회논문지
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• 제15권8호
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• pp.5195-5200
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• 2014

최근 백색 LED는 각종 조명등의 응용 시스템에 크게 사용되고 있다. 백색 LED 칩을 만들기 위하여 실리콘과 형광체를 배합하여 청색 LED 칩 위에 도포하는 공정이 필요한데, 이때 배합의 오류, 실리콘의 상온 노출 시간의 경과, 청색 칩 특성의 변화 등의 원인으로 버려지는 형광체가 있어 이것이 원가 절감에 악영향을 미치고 있다. 본 연구에서는 버려지는 형광체의 재생공정을 통하여 제조된 LED와 정상형광체의 LED의 특성을 비교하고, 이들을 이용하여 실 응용 제품인 LED 손전등에 적용하여 그 특성의 동일함을 얻었다. 재생과 정상 형광체의 특성에서 광량 저하량 3.2[Cd]와 3.6[Cd], 색감 저하량 57[K]와 58[K]를 보였고, LED의 실제 응용제품에 적용한 결과 최대 백색파장 444.3[nm]와 449.8[nm]를 나타내어 재생형광체의 LED가 정상의 것과 동일한 특성을 보여 원가절감에 큰 기여를 할 것으로 나타났다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.92-92
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• 2010

Replacing the existing illumination with solid-state lighting devices, such as light-emitting diodes (LEDs) are expected to reduce energy consumption and environmental pollution as they provide better efficiency and longer lifetimes. Currently, white light emitting diodes are composed of UV or blue LED with down-converting materials such as highly luminescent phosphors White light-emitting diodes (LED) were fabricated with multi-shell nanocrystal quantum dots for enhanced luminance and improved stability over time. Multi-shell quantum dots (QDs) were synthesized through one pot process by using the Successive Ionic Layer Adsorption and Reaction (SILAR) method. As prepared, the multi-shell QD has cubic lattice of zinc-blend structure with semi-spherical shape with quantum yield of higher than 60 % in solution. Further, highly fluorescent multi-shell QD was deposited on the blue LED, which resulted in QD-based white LED with high luminance with excellent color rendering properties.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.189-189
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• 2016

Recently, many researchers have shown an increased interest in colloidal quantum dots (QDs) due to their unique physical and optical properties of size control for energy band gap, narrow emission with small full width at half maxima (FWHM), broad spectral photo response from ultraviolet to infrared, and flexible solution processing. QDs can be widely used in the field of optoelectronic and biological applications and, in particular, colloidal QDs based light emitting diodes (QDLEDs) have attracted considerable attention as an emerging technology for next generation displays and solid state lighting. A few methods have been proposed to fabricate white color QDLEDs. However, the fabrication of white color QDLEDs using single QD is very challenging. Recently, hybrid nanocomposites consisting of CdTe/ZnO heterostructures were reported by Zhimin Yuan et al.[1] Here, we demonstrate a novel but facile technique for the synthesis of CdTe/ZnO/G.O(graphene oxide) quasi-core-shell-shell quantum dots that are applied in the white color LED devices. Our best device achieves a maximum luminance of 484.2 cd/m2 and CIE coordinates (0.35, 0.28).

• 한국세라믹학회지
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• 제51권6호
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• pp.533-538
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• 2014

Today, silicon and epoxy resin are used as materials of conversion lenses for white LEDs on the basis of their good bonding and transparency in LED packages. But these materials give rise to long-term performance problems such as reaction with water, yellowing transition, and shrinkage by heat. These problems are major factors underlying performance deterioration of LEDs. In this study, in order to address these problems, we fabricated a conversion lenses using glass, which has good chemical durability and is stable to heat. The fabricated conversion lenses were applied to a remote phosphor type. In this experiment, the conversion lens for white LED was coated on a glass substrate by a screen printing method using paste. The thickness of the coated conversion lens was controlled during 2 or 3 iterations of coating. The conversion lens fabricated under high heat treatment temperature and with a thin coating showed higher luminance efficiency and CCT closer to white light than fabricated lenses under low heat treatment temperature or a thick coating. The conversion lens with $32{\mu}m$ coating thickness showed the best optical properties: the measured values of the CCT, CRI, and luminance efficiency were 4468 K, 68, and 142.22 lm/w in 20 wt% glass frit, 80 wt% phosphor with sintering at $800^{\circ}C$.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권4호
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• pp.275-285
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• 2012

This paper presents a changes of luminescence property for converted white LEDs with the commercially available silicate phosphor. If silicate phosphor's quantity increase step by step. luminescence property will be changing. we analyze luminescence property for these change and carry out the high temperature aging test for 7,000 hours, the high temperature and humidity aging test for 7,000 hours for reliability. LED degradation not only results in reduced light output but also in color changes. so we monitor correlated color temperature (CCT), chromaticity coordinates(x, y) and spectrum intensity. Those results suggest that humidity factor more bad effect in color changes than temperature factor and Lighting quality is related with quantity of phosphor.

• 조명전기설비학회논문지
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• 제23권12호
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• pp.10-22
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• 2009

본 논문은 독립적으로 LED의 색온도와 조도를 제어하는 알고리즘과 이를 이용한 LED 조명 시스템을 제안한다. 제안된 알고리즘이 항상 해를 가지는 것을 증명해 제안된 알고리즘이 유효함을 보여주었다. 적색, 녹색, 청색, 백색 (RGBW) LED를 사용한 LED 모듈 제어에 제안된 알고리즘을 적용하였다. 이 모듈의 색온도는 3,500~7,500[$^{\circ}K$], 조도는 500~1,500[lux] 범위에서 변화했다. LED의 접합온도가 40[$^{\circ}C$]로 유지될 때, 이 범위 내에서 색온도와 조도의 편차는 0.8[%] 이하였다. 30~70[$^{\circ}C$]의 범위에서는 목표 조도와 색온도가 각각 1,000[lux]와 6,500[$^{\circ}K$] 일 때 조도와 색온도의 편차가 2.1[%]와 3.1[%] 이하이고, 온도 보상된 경우에는 편차가 1[%]와 0.49[%] 이하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.50-51
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• 2009

Nitride Phosphors have recently been considered as a novel class of luminescent materials for white LEDs due to their promising luminescent properties. It is of great importance to tailor the emission color in order to meet the requirements for practical applications. The paper presents the results of tuning the emission colors of sialon phosphors through compositional tailoring.