Packaging of Phosphor Based High Power White LEDs: Effects of Phosphor Concentration and Packaging Configuration

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Yuan-Chang Lin ◽  
Jiun Pyng You ◽  
Nguyen T. Tran ◽  
Yongzhi He ◽  
Frank G. Shi
Keyword(s):  
Optical Power ◽  
Luminous Efficiency ◽  
Color Temperature ◽  
Light Emitting ◽  
White Leds ◽  
Chromaticity Coordinate ◽  
Air Interface ◽  
Output Only ◽  
White Light Emitting Diodes ◽  
Color Rendering

Two types of packaged white light emitting diodes in which one has a flat-top (FT) emitting surface and the other is a flat-top-with-lens (FTWL) type are fabricated by using the same leadframe and investigated on their optical properties, such as optical power, luminous efficiency, correlated color temperature (CCT), chromaticity coordinate, and color-rendering index (CRI), as a function of phosphor concentration in silicone encapsulant. It is found out that the optical power, CRI, and CCT decrease steadily as the phosphor ratio increases, while the luminous efficiency increases up to a level and then drops after a certain value of the phosphor ratio for both types of packages. Due to the totally internal reflection (TIR) at the encapsulant-air interface, the FT package shows a 10∼11% power (in mW) reduction compared with the FTWL package at the same phosphor concentration. However, it is demonstrated that the FT package provides a more efficient way of utilizing phosphor than the FTWL package based on the same targeted chromaticity coordinates due to the TIR effect inside, resulting in a reduced phosphor usage with a lumen output only about 3% lower than that of the FTWL package.

scholarly journals Light Output, Thermal Properties, and Reliability of Using Glass Phosphors in WLED Packages

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 239
Author(s):  
Chin-Chuan Huang ◽  
Tsung-Han Weng ◽  
Chun-Liang Lin ◽  
Yan-Kuin Su
Keyword(s):  
Thermal Properties ◽  
Yttrium Aluminum Garnet ◽  
Saturated Vapor ◽  
Light Output ◽  
Junction Temperature ◽  
Color Temperature ◽  
Light Emitting ◽  
Chromaticity Coordinate ◽  
White Light Emitting Diodes ◽  
Color Rendering

White-light-emitting diodes (WLED) based on yttrium aluminum garnet (YAG) phosphors sintered with glass (PiG) and with silicone (PiS) are compared in terms of their light properties, temperature properties and reliability.The complete YAG phosphor was doped with an encapsulant traditional WLED (PiS WLED), and the WLED was covered with PiG (PiG WLED). PiG was made by sintering glass powder and YAG phosphor at the ratio of 87:13 (%), and the correlated color temperature (CCT) was 5564 K. The CCT of the PiG WLED with the YAG doping concentration of 8.5 wt.% approximated 5649 K. The initial light output of the PiG WLED was 6.4% lower than that of the PiS WLED. Under 1008 h and 350 mA aging, PiG WLED and PiS WLED’ light output, CCT and color rendering index variation rates were all within 1%. In the saturated vapor-pressure test, no sample exhibited red ink infiltration, light nor peeling between the encapsulant and the lead-frame. Compared with that of the PiS WLED, the junction temperature of the PiG WLED reduced from 88.4 °C to 81.3 °C. Thermal resistance dropped from 37.4 °C/W to 35.6 °C/W. The PiG WLED presented a better CIE (Commission Internationale de l’Eclairage) 1931 chromaticity coordinate (x,y) concentration and thermal properties than the PiS WLED.

scholarly journals Novel lighting properties of white LEDs with two-layered remote phosphor package using red-emitting α-SrO·3B2O3:Sm2+ phosphor

2017 ◽  
Vol 35 (3) ◽  
pp. 618-625
Author(s):  
Tran Hoang Quang Minh ◽  
Nguyen Huu Khanh Nhan ◽  
Nguyen Doan Quoc Anh ◽  
Hsiao-Yi Lee
Keyword(s):  
Lower Layer ◽  
Luminous Flux ◽  
Color Temperature ◽  
Phosphor Layer ◽  
Light Emitting ◽  
White Leds ◽  
Color Uniformity ◽  
Remote Phosphor ◽  
White Light Emitting Diodes ◽  
Color Rendering

AbstractThis paper investigates a method for improving the lighting performance of white light-emitting diodes (WLEDs), packaged using two separating remote phosphor layers, yellow-emitting YAG:Ce phosphor layer and red-emitting α-SrO·3B2O3:Sm2+ phosphor layer. The thicknesses of these two layers are 800 μm and 200 μm, respectively. Both of them have been examined at average correlated color temperatures (CCT) of 7700 K and 8500 K. For this two-layer model, the concentration of red phosphor has been varied from 2 % to 30 % in the upper layer, while in the lower layer the yellow phosphor concentration was kept at 15 %. It was found interesting that the lighting properties, such as color rendering index (CRI) and luminous flux, are enhanced significantly, while the color uniformity is maintained at a level relatively close to the level in one-layer configuration (measured at the same correlated color temperature). Besides, the transmitted and reflected light of each phosphor layer have been revised by combining Kubelka-Munk and Mie-Lorenz theories. Through the analysis, it is demonstrated that the packaging configuration of two-layered remote phosphor that contains red-emitting α-SrO·3B2O3:Sm2+ phosphor particles provides a practical solution to general WLEDs lighting.

scholarly journals Preparation of Bismuth Oxide Photocatalyst and Its Application in White-light LEDs

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Yen-Chang Chu ◽  
Gang-Juan Lee ◽  
Chin-Yi Chen ◽  
Shih-Hsin Ma ◽  
Jerry J. Wu ◽  
...  
Keyword(s):  
Bismuth Oxide ◽  
White Light ◽  
Front Surface ◽  
Color Temperature ◽  
Spray Pyrolysis Method ◽  
Light Emitting ◽  
White Leds ◽  
Air Purifier ◽  
Cie Chromaticity ◽  
White Light Emitting Diodes

Bismuth oxide photocatalysts were synthesized and coated on the front surface of phosphor-converted white light-emitting diodes to produce a safe and environmentally benign lighting source. Bismuth oxide photocatalyst powders were synthesized with a spray pyrolysis method at 500°C, 600°C, 700°C, and 800°C. Using the absorption spectrum in the blue and UV regions of the bismuth oxide photocatalysts, the blue light and UV leakage problems of phosphor-converted white LEDs can be significantly reduced. The experimental results showed that bismuth oxide photocatalyst synthesized at 700°C exhibited the most superior spectrum inhibiting ability. The suppressed ratio reached 52.33% in the blue and UV regions from 360 to 420 nm. Related colorimetric parameters and the photocatalyst decomposition ability of fabricated white-light LEDs were tested. The CIE chromaticity coordinates(x,y)were (0.349, 0.393), and the correlated color temperature was 4991 K. In addition, the coating layer of photocatalyst can act as an air purifier and diffuser to reduce glare. A value of66.2±0.60 ppmv of molecular formaldehyde gas can be decomposed in 120 mins.

scholarly journals A broadband cyan-emitting Ca2LuZr2(AlO4)3:Ce3+ garnet phosphor for near-ultraviolet-pumped warm-white light-emitting diodes with an improved color rendering index

2020 ◽  
Vol 8 (3) ◽  
pp. 1095-1103 ◽  
Author(s):  
Liangling Sun ◽  
Balaji Devakumar ◽  
Jia Liang ◽  
Shaoying Wang ◽  
Qi Sun ◽  
...  
Keyword(s):  
White Light ◽  
Light Emitting Diodes ◽  
Emission Spectra ◽  
Light Emitting ◽  
White Leds ◽  
Near Ultraviolet ◽  
Warm White Light ◽  
Color Rendering Index ◽  
White Light Emitting Diodes ◽  
Color Rendering

Broadband cyan-emitting Ca2LuZr2(AlO4)3:Ce3+ garnet phosphors enabled to fill the cyan gap in the emission spectra of near-ultraviolet-pumped warm-white LEDs, thus resulting in improved color rendering index.

A NEW RED PHOSPHOR OF THE Mn ACTIVATED NON-STOICHIOMETRIC STRONTIUM ALUMINATE 3SrO•5Al2O3 FOR HIGH COLOR RENDERING WHITE LEDS

2013 ◽  
Vol 06 (03) ◽  
pp. 1350028 ◽  
Author(s):  
LEI CHEN ◽  
YAO ZHANG ◽  
FAYONG LIU ◽  
XIAORONG DENG ◽  
SHAOCHAN XUE ◽  
...  
Keyword(s):  
Dipole Interaction ◽  
Critical Distance ◽  
Sem Analysis ◽  
Strontium Aluminate ◽  
Red Phosphor ◽  
Light Emitting ◽  
White Leds ◽  
Warm White Light ◽  
White Light Emitting Diodes ◽  
Color Rendering

A new red phosphor of strontium aluminate activated by Mn4+ was developed for high color rendering and warm white light-emitting diodes. The phosphor composition and conditions for synthesis were optimized through solid-state reaction. Meanwhile, the structure and morphology were investigated with XRD and SEM analysis. The results show that the 3SrO•5Al2O3 activated by 0.0005 M Mn fired at 1300°C in air ambient by adopting 2.5 wt.% AlF3 as flux exhibits most efficient luminescence. A white LED device prototype with CIE (0.3291, 0.3571), CCT 5639 K, CRI Ra 92.6, and efficacy 63 lm/W driven at 20 mA has been packaged by pre-coating the red phosphor combined with a yellow one Y3Al5O12:Ce3+ on a blue InGaN chip. The analysis of critical distance and luminescence quench reveal that the mechanism of energy transfer for luminescence is through dipole–dipole interaction.

Compatibility of Photoluminescence Properties in ScPO4:Eu3+, Tb3+ Phosphor for White Light Emitting Diodes

2021 ◽  
Vol 21 (12) ◽  
pp. 5890-5895
Author(s):  
Jian Zhou ◽  
Jian-Wen Zhao ◽  
Si-Li Ren ◽  
Jun Dong
Keyword(s):  
The Body ◽  
Color Temperature ◽  
White Led ◽  
Photoluminescence Properties ◽  
Light Emitting ◽  
Co Doping ◽  
Emission Color ◽  
Single Matrix ◽  
White Light Emitting Diodes ◽  
Color Rendering

ScPO4:Eu3+, Tb3+ phosphors with tuned emission color were prepared through high temperature solid-state reaction. The structure, morphology and photoluminescence properties of the title samples were collected by XRD, SEM and fluorescence spectrophotometer, respectively. Co-doping Eu3+ and Tb3+ in ScPO4 does not change the body-centered tetragonal structure of the host. And the morphology remains essentially unchanged except for slight agglomeration. Changing the ratio of Tb3+/Eu3+, the tuned emission can be achieved, the color could be adjusted from green through yellow to orange-red. The ScPO4:0.03Tb3+, 0.03Eu3+ phosphor with high thermal stability as the single matrix phosphor can be suitable for the NUV-pumped white LED. The white LED with a color rendering index of 86.5 and a correlated color temperature of 3470 K has been generated by packaging BAM:Eu2+ with ScPO4:0.03Tb3+, 0.03Eu3+ on an NUV-InGaN chip.

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