• Title/Summary/Keyword: Yellow phosphors

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Luminescent Characteristics of Bi Co-doped ZnS:Mn Yellow Phosphors for White Light Emitting Diodes (Bi를 첨가한 백색 LED용 ZnS:Mn 황색형광체의 발광특성)

  • Jung, Jong-Hun;Yu, Il
    • Korean Journal of Materials Research
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    • v.21 no.1
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    • pp.46-49
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    • 2011
  • Bi co-doped ZnS:Mn,Bi yellow phosphors for white light emitting diodes were prepared by the conventional solidstate reaction method. The optical and structural properties of ZnS:Mn,Bi phosphors were investigated by x-ray diffraction, scanning electro microscopy and photoluminescence. ZnS:Mn,Bi phosphors showed XRD patterns of hexagonal structure. The photoluminescence of ZnS:Mn,Bi phosphors showed spectra extending from 480 to 700 nm, peaking at 580 nm. The photoluminescence of 580 nm in the ZnS:Mn,Bi phosphors was associated with the 4T1 ${\rightarrow}$ 6A1 transition of the Mn2+ ions. The highest photoluminescent intensity of the phosphors under 405 nm and 450 nm excitation was obtained at Bi concentration of 7mol%. The optimum mixing conditions with epoxy and yellow phosphor for white light emitting diodes were observed in a ratio of epoxy:yellow phosphor of 1:3.5. The CIE chromaticity of the white LED at the 1:3.5 ratio was X = 0.3454 and Y = 0.2449.

Luminescent Characteristics of ZnS:Mn,Cu Yellow Phosphors for White Light Emitting Diodes (백색 LED용 ZnS:Mn,Cu 황색형광체의 발광특성)

  • Yu, Il;Lee, Ji-Young
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.8
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    • pp.627-631
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    • 2010
  • ZnS:Mn yellow phosphors doped with Cu for white light emitting diodes were synthesized by solid state reaction method. The optical properties and structures of ZnS:Mn,Cu phosphors were investigated by x-ray diffraction, photoluminescence, and scanning electro microscopy. Photoluminescence excitation spectra originated from $Mn^{2+}$ were ranged from 450 nm to 500 nm. The yellow emission at around 580 nm was associated with $^4T_1{\rightarrow}^6A_1$ transition of $Mn^{2+}$ ions in ZnS:Mn,Cu phosphors. The highest photoluminescence intensity of the phosphors under 405 nm excitation was obtained at Cu concentration of 0.02 mol%. The enhanced photoluminescent intensity in the ZnS:Mn,Cu phosphors was interpreted by energy transfer from Cu to Mn.

Nitride Phosphors for the Better Performance of WLEDs

  • Yoon, Chul-Soo
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.49-49
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    • 2009
  • Phosphors with oxide host material, YAG:$Ce^{3+}$ and $(Ca,Sr,Ba)_2SiO_4:Eu^{2+}$ yellow phosphor, has been used for LED applications. The WLEDs using these phosphors are widely used for LCD backlighting, automobile, and general lighting applications since they have high conversion efficiency and good thermal and chemical stability which can meet necessary life time of LED products up to now. With advances of LED chip technology, the external quantum efficiency and driving current in chip get higher so that the phosphors for high power chip are required to maintain high conversion efficiency and stability at high temperature due to the heat dissipated from LED chips. In addition, higher color rendering index of LED lighting and color reproducibility of LCD than those of LEDs with single yellow phosphors are required. In order to overcome these technical issues rising from evolution of LED technology, new phosphors are in demand and nitride phosphors, one of the promising new candidate materials, will be discussed here.

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Luminescent characteristic of ZnS:Mn,Cu yellow phosphors for Light Emitting Diodes (백색 LED용 ZnS:Mn,Cu 황색 형광체의 발광 특성)

  • Lee, Ji-Young;Yu, Il
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.06a
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    • pp.141-141
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    • 2010
  • ZnS:Mn yellow phosphors doped with Cu for white light emitting diodes were synthesized by solid state reaction method. Photoluminescence excitation spectra originated from $Mn^{2+}$ were ranged from 450 nm to 500 nm. The yellow emission at around 580 nm was associated with $^4T_1{\rightarrow}^6A_1$ transition of $Mn^{2+}$ ions in ZnS:Mn,Cu phosphors. The highest photoluminescence intensity of the phosphors under 405 nm excitation was obtained at Cu concentration of 0.02 mol%.

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Effect of ZnS:Mn, Dy Yellow Phosphor on White LEDs Characteristics (백색 LED의 특성에 대한 ZnS:Mn, Dy 황색 형광체의 영향)

  • Shin, Deuck-Jin;Yu, Il
    • 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.

The Optical Properties of(Y1-xGdx)3-z(Al1-yGay)5O12:CezPhosphors for White LED

  • Huh, Young-Duk;Cho, Young-Shik;Do, Young-Rag
    • Bulletin of the Korean Chemical Society
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    • v.23 no.10
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    • pp.1435-1454
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    • 2002
  • Bright yellow ${(Y_{1-x}Gd_x)}_{3-z}{(Al_{1-y}Ga_y)}_5O_{12}:Ce_z$ phosphors were synthesized. White LED was obtained by the combination of non-absorbed blue emission from a blue L ED itself and yellow emission from ${(Y_{1-x}Gd_x)}_{3-z}{(Al_{1-y}Ga_y)}_5O_{12}:Ce_z$ phosphors. The crystal structures and optical properties of ${(Y_{1-x}Gd_x)}_{3-z}{(Al_{1-y}Ga_y)}_5O_{12}:Ce_z$ phosphors were investigated.

Effect of Chip Wavelength and Particle Size on the Performance of Two Phosphor Coated W-LEDs

  • Yadav, Pooja;Joshi, Charusheela;Moharil, S.V.
    • Transactions on Electrical and Electronic Materials
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    • v.15 no.2
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    • pp.66-68
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    • 2014
  • Most commercial white LED lamps use blue chip coated with yellow emitting phosphor. The use of blue excitable red and green phosphors is expected to improve the CRI. Several phosphors, such as $SrGa_2S_4:Eu^{2+}$ and $(Sr,Ba)SiO_4:Eu^{2+}$, have been suggested in the past as green components. However, there are issues of the sensitivity and stability of such phosphors. Here, we describe gallium substituted $YAG:Ce^{3+}$ phosphor, as a green emitter. YAG structures are already accepted by the industry, for their stability and efficiency. LEDs with improved CRI could be fabricated by choosing $Y_3Al_4GaO_{12}:Ce^{3+}$ (green and yellow), and $SrS:Eu^{2+}$ (red) phosphors, along with blue chip. Also, the effect of a slight change in chip wavelength is studied, for two phosphor-coated w-LEDs. The reduction in particle size of the coated phosphors also gives improved w-LED characteristics.

Luminescent Characteristics of ZnS:Mn,Sm Phosphors Prepared with Various Sm Concentration for White Light Emitting Diodes (Sm 농도변화에 따른 백색 LED용 ZnS:Mn,Sm형광체의 발광특성)

  • Lee, Ji-Young;Lee, Sang-Jae;Kim, Tae-Woo;Yu, Il
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.1
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    • pp.27-31
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    • 2011
  • ZnS:Mn yellow phosphors doped with Sm for white light emitting diodes were synthesized by solid state reaction method. These sample showed the characteristic X-ray diffraction patterns for main peak (110) of ZnS:Mn,Sm. Photoluminescence excitation spectra originated from $Mn^{2+}$ were ranged from 450 nm to 500 nm. The yellow emission at around 580 nm was associated with $^4T_1{\rightarrow}^6A_1$ transition of $Mn^{2+}$ ions in ZnS:Mn,Sm phosphors. The highest photolum inescence intensity of the phosphors under 405 nm and 450 nm excitation was obtained at Sm concentration of 1 mol%. The enhanced photoluminescent intensity in the ZnS:Mn,Sm phosphors was interpreted by energy transfer from Sm to Mn. The highest luminescent intensity of white LED was obtained at the epoxy-to-yellow phosphor ratio of 1:3. At this ratio, the CIE chromaticity of the white LED was X=0.3886 and Y=0.2928.

Synthesis and Optical Properties of Ca1-xSrxS:Mn Phosphors (Ca1-xSrxS:Mn 형광체의 합성과 광 특성)

  • Sung, Hye-Jin;Huh, Young-Duk
    • Korean Journal of Materials Research
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    • v.17 no.3
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    • pp.137-141
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    • 2007
  • A series of $Ca_{1-x}Sr_{x}S:Mn$ phosphors were synthesized by solid-state reactions. The emission peaks of $Ca_{1-x}Sr_{x}S:Mn$ is blue shifted front 605 to 570 nm with increasing Sr content. Since $Ca_{1-x}Sr_{x}S:Mn$. Mn phosphors exhibit strong absorption in region of 254 nm, the emission wavelength of a fluorescent lamp, these phosphors can be used as wavelength tunable emitting phosphors from reddish orange to yellow. We investigated the optical and structural properties of $Ca_{1-x}Sr_{x}S:Mn$ phosphors.

Microwave-Modified Sol-Gel Process for Microcystalline KY(WO4)2: Ho3+/Yb3+ Phosphors and their Upconversion Photoluminescence Properties

  • Lim, Chang Sung
    • Journal of the Korean Ceramic Society
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    • v.52 no.6
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    • pp.514-520
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    • 2015
  • $KY_{1-x}(WO_4)_2:Ho^{3+}/Yb^{3+}$ yellow phosphors with doping concentrations of $Ho^{3+}$ and $Yb^{3+}$ ($x=Ho^{3+}+Yb^{3+}$, $Ho^{3+}=0.05$, 0.1, 0.2 and $Yb^{3+}=0.2$, 0.45) were successfully prepared using the microwave-modified sol-gel method; their upconversion (UC) photoluminescence properties were investigated in detail. Well-crystallized particles, formed after heat-treatment at $900^{\circ}C$ for 16 h, showed a fine and homogeneous morphology with particle sizes of $2-5{\mu}m$. Under excitation at 980 nm, the UC $KY_{0.7}(WO_4)_2:Ho_{0.1}Yb_{0.2}$ and $KY_{0.5}(WO_4)_2Ho_{0.05}Yb_{0.45}$ particles exhibited excellent yellow emissions based on a strong 545-nm emission band in the green region and a very strong 655-nm emission band in the red region. Pump power dependence and Commission Internationale de L'Eclairage chromaticity of the UC emission intensity were evaluated. The spectroscopic properties were examined comparatively using Raman spectroscopy.