Enhancing of correlated color temperature uniformity for multi-chip white-light LEDs by adding SiO2in phosphor layer

2014 ◽  
Vol 38 (3) ◽  
pp. 297-303 ◽  
Author(s):  
Nguyen Doan Quoc Anh ◽  
Min-Feng Lai ◽  
Hsin-Yi Ma ◽  
Hsiao-Yi Lee
Keyword(s):  
White Light ◽  
Color Temperature ◽  
Temperature Uniformity ◽  
Phosphor Layer

Cylindrical Tuber Encapsulant Layer Realization by Patterned Surface for Chip-on-Board Light-Emitting Diodes Packaging

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Xingjian Yu ◽  
Run Hu ◽  
Ruikang Wu ◽  
Bin Xie ◽  
Xiaoyu Zhang ◽  
...  
Keyword(s):  
Blue Light ◽  
White Light ◽  
Light Emitting Diodes ◽  
Composite Layer ◽  
Color Temperature ◽  
Efficiency Enhancement ◽  
Phosphor Layer ◽  
Light Emitting ◽  
Nanosilica Particles ◽  
Light Efficiency

In this study, we realized a cylindrical tuber silicone layer for improving the light efficiency of chip-on-board light-emitting diodes (COB-LEDs) by fabricating patterned LED substrate with both silicone-wetting and silicone-repellency surfaces. To realize silicone-repellency surface, low surface energy modified nanosilica particles were prepared and deposited on the LED substrate to form porous hierarchical structure. Light efficiency enhancement for blue light COB-LEDs with pure cylindrical tuber silicone layer and white light COB-LEDs with phosphor–silicone composite layer was studied. The results show that for blue light COB-LEDs with pure cylindrical tuber silicone layer, the light efficiency increases with the contact angle and a highest light efficiency enhancement of 62.6% was achieved at 90 deg when compared to the flat silicone layer. For white light COB-LEDs at correlated color temperature (CCT) of ∼5500 K, the cylindrical tuber silicone layer enhances the light efficiency by 13.6% when compared to the conventional flat phosphor layer.

scholarly journals Applying SiO2 nano-particles for improving optical properties of WLED conformal and in-cup structures

2021 ◽  
Vol 10 (4) ◽  
pp. 1914-1922
Author(s):  
Phan Xuan Le ◽  
Pham Quang Minh
Keyword(s):  
Luminous Flux ◽  
Luminous Efficiency ◽  
Nano Particles ◽  
Color Temperature ◽  
Temperature Uniformity ◽  
Phosphor Layer ◽  
Temperature Deviation ◽  
Color Uniformity ◽  
Remote Phosphor ◽  
Index Ratio

This article is the analysis of SiO2 nano-particles’ influences on the luminous efficiency and the color temperature uniformity of a remote phosphor structure in a WLED. The purpose of integrating SiO2 into the silicone layer in the remote phosphor structure is to significantly promote the scattering occurrences. Particularly, with an appropriate proportion of SiO2, there could be more blue lights generated at large angles, leading to reducing the angular-dependent color temperature deviation. The luminous flux also can get benefits from SiO2 addition owing to a proper air-phosphor layer refractive index ratio provided by this SiO2/silicone compound. The attained experimental results were compared with optical values of a non-SiO2 remote phosphor configuration and showed a notable enhancement. The color deviation was reduced by approximately 600 K in the angles from -700 ­to 700. Additionally, the lumen efficiency was improved by 2.25% at 120 mA driving current. Hence, SiO2 can be used to boost both color uniformity and luminous efficacy for remote-phosphor WLED.

Color Uniformity Enhancement of White Light-Emitting Diodes With Novel Bell Shape Phosphor Layer

2017 ◽  
Author(s):  
Xingjian Yu ◽  
Weicheng Shu ◽  
Bofeng Shang ◽  
Bin Xie ◽  
Yanhua Cheng ◽  
...  
Keyword(s):  
White Light ◽  
Light Emitting Diodes ◽  
Color Temperature ◽  
Phosphor Layer ◽  
Spherical Cap ◽  
Light Emitting ◽  
Vof Model ◽  
Color Uniformity ◽  
Coating Method ◽  
White Light Emitting Diodes

In this study, we proposed a bell shape phosphor layer geometry and the corresponding dual-step phosphor coating method for enhancing the angular color uniformity (ACU) of phosphor-converted white light-emitting diodes (pcLEDs). Numerical simulation based on Volume of Fluid (VOF) model was applied to predict phosphor geometries. Based on the simulated results, experiments were conducted to realize the phosphor geometries. The simulated results show that the VOF model can predict the phosphor geometries with an acceptable geometric deviation within 5%. The experimental results show that compared with the spherical cap phosphor layer geometry, the bell shape geometry can achieve better ACU performance, an optimal bell phosphor layer geometry with equal coating volume above and around the LED chip was achieved, for the corrected color temperature (CCT) of 4000 K, the angular CCT deviation of the optimal geometry is 62 K, while it is 382 K for the spherical cap geometry.

scholarly journals Improving the optical efficiency of white light-emitting diodes based on phosphor-in-glass by a dual-layer remote phosphorus structure with the application of LiLaO2:Eu3+ and CaSO4:Ce3+, Mn2+

2021 ◽  
Vol 10 (4) ◽  
pp. 1838-1845
Author(s):  
Phan Xuan Le ◽  
Le Tien
Keyword(s):  
White Light ◽  
Mie Scattering ◽  
Luminous Flux ◽  
Color Temperature ◽  
Phosphor Layer ◽  
Green Phosphor ◽  
Optical Efficiency ◽  
Color Quality ◽  
Color Uniformity ◽  
Remote Phosphor

While the remote phosphor structure is not an appropriate solution for WLED color uniformity, it is more advantageous for the luminous output of WLED than the conformal phosphor or in-cup phosphor structure. Acknowledging the ability of the remote phosphor structure, many studies have been carried out to surmount the color quality disadvantage of this structure. A dual-layer remote phosphor configuration is proposed in this research paper to acquire better color quality for WLEDs through heightening the color rendering index (CRI) and the color quality scale (CQS). The color temperature of the WLED packages this study is 8500 K. By inserting a layer of green CaSO4:Ce3+,Mn2+ or red LiLaO2:Eu3+ phosphor on the yellow YAG:Ce3+ phosphor layer, the phosphor structure configuration can be constructed. Then, to get the best color quality, the concentration of added phosphor LiLaO2:Eu3+ would be changed. The findings showed the rise of CRI and CQS along with the LiLaO2:Eu3+, which implies the influence of LiLaO2:Eu3+ to the growth of red light components within WLEDs packages. The greater the concentration of LiLaO2:Eu3+ is, the more the CRI and CQS increase. Meanwhile, the luminous flux gains from the green phosphor CaSO4:Ce3+,Mn2+. Nevertheless, the luminous flux and color quality would decrease if the concentrations of both red LiLaO2:Eu3+ and green CaSO4:Ce3+,Mn2+ phosphors reach a certain corresponding level. Centered on the Mie-scattering theory and the law of Lambert-Beer, this result is illustrated. The findings in this research are vital references for manufacturing WLEDs with higher white light performance.

scholarly journals Enhancing light scattering effect of white LEDs with ZnO nanostructures

2021 ◽  
Vol 11 (5) ◽  
pp. 3838
Author(s):  
My Hanh Nguyen Thi ◽  
Nguyen Thi Phuong Loan ◽  
Hoang Van Ngoc
Keyword(s):  
Scattered Light ◽  
Fdtd Method ◽  
Color Temperature ◽  
Temperature Uniformity ◽  
Yellow Light ◽  
Phosphor Layer ◽  
White Leds ◽  
Color Quality ◽  
Small Decline ◽  
Difference Time

Pc-LEDs, the lighting method that blends blue LED light with yellow light from phosphor to discharge white radiation, is one of the most advance known for high lumen output. However, pc-LEDs has inferior due to angular CCT deviation, which prevent pc-LEDs from reaching better performance. As a result, this research is conducted to address the need of pc-LEDs development by introducing a configuration doped with ZnO nanoparticles. The finite-difference time-domain (FDTD) method and the phosphor layer containing ZnO were applied in the experiments. The effect of ZnO-filled on the performance of color quality pc-LEDs is confirmed through calculated results. In particular, the uniformity of scattered light is improved with the presence of ZnO. In addition, ZnO particles also minimize the deviation of color temperature and enhance the color quality. Although there is a small decline in lumen output to achieve better color temperature uniformity, however, with suitable concentrations such as 0.25% N-ZnO, 0.25% S-ZnO, and 0. 75% R-ZnO, the decline is acceptable. The research on ZnO pc-LEDs demonstrates that this affordable and simple configuration can improve lighting properties and create other directions to enhance white light

scholarly journals Near Unity PLQY and High Stability of Barium Thiocyanate Based All-Inorganic Perovskites and Their Applications in White Light-Emitting Diodes

Photonics ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 209
Author(s):  
Gopi Chandra Adhikari ◽  
Saroj Thapa ◽  
Yang Yue ◽  
Hongyang Zhu ◽  
Peifen Zhu
Keyword(s):  
White Light ◽  
Large Scale ◽  
Light Emitting Diode ◽  
Photophysical Properties ◽  
Environmental Stability ◽  
Color Temperature ◽  
Ambient Atmosphere ◽  
Light Emitting ◽  
Halide Perovskite ◽  
Lead Halide

All-inorganic lead halide perovskite (CsPbX3) nanocrystals (NCs) have emerged as a highly promising new generation of light emitters due to their extraordinary photophysical properties. However, the performance of these semiconducting NCs is undermined due to the inherent toxicity of lead and long-term environmental stability. Here, we report the addition of B-site cation and X-site anion (pseudo-halide) concurrently using Ba(SCN)2 (≤50%) in CsPbX3 NCs to reduce the lead and improve the photophysical properties and stability. The as-grown particles demonstrated an analogous structure with an almost identical lattice constant and a fluctuation of particle size without altering the morphology of particles. Photoluminescence quantum yield is enhanced up to near unity (~98%) by taking advantage of concomitant doping at the B- and X-site of the structure. Benefitted from the defect reductions and stronger bonding interaction between Pb2+ and SCN− ions, Ba(SCN)2-based NCs exhibit improved stability towards air and moisture compared to the host NCs. The doped NCs retain higher PLQY (as high as seven times) compared to the host NCs) when stored in an ambient atmosphere for more than 176 days. A novel 3D-printed multiplex color conversion layer was used to fabricate a white light-emitting diode (LED). The obtained white light shows a correlated color temperature of 6764 K, a color rendering index of 87, and luminous efficacy of radiation of 333 lm/W. In summary, this work proposes a facile route to treat sensitive lead halide perovskite NCs and to fabricate LEDs by using a low-cost large-scale 3-D printing method, which would serve as a foundation for fabricating high-quality optoelectronic devices for near future lighting technologies.

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