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.

Numerical and Experimental Study on the Transferred Volume in Phosphor Dip-Transfer Coating Process of Light-Emitting Diodes Packaging

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Bofeng Shang ◽  
Xingjian Yu ◽  
Huai Zheng ◽  
Bin Xie ◽  
Qi Chen ◽  
...  
Keyword(s):  
High Speed ◽  
Light Emitting Diodes ◽  
Relative Difference ◽  
Volume Control ◽  
Light Emitting ◽  
Withdrawal Speed ◽  
Vof Model ◽  
Color Uniformity ◽  
Coating Method ◽  
White Light Emitting Diodes

The phosphor dip-transfer coating method is simple and flexible for transferring a pre-analyzed volume of phosphor gel, which can be beneficial to the high angular color uniformity (ACU) of white light-emitting diodes (LEDs). The crux of this method is the volume control of the phosphor gel; however, the critical factors which influence the volume control remain unrevealed. In this paper, we concentrate on investigating the transferred volume in terms of three parameters: withdrawal speed, post radius, and dipping depth. Numerical simulations were carried out utilizing the volume of fluid (VOF) model combined with the dynamic mesh model. The experiments were also conducted on an optical platform equipped with a high-speed camera. The simulation results coincide well with the experimental results, with the maximum relative difference within 15%. The results show that the transferred volume increases with the increasing withdrawal speed and remains stable when the speed is greater than 1 mm/s, and it shows a linear relationship with the cube of post radius. And the transferred volume will increase with the dipping depth. Based on the experimental and numerically work, it is concluded that the volume of the pre-analyzed phosphor gel can be precisely obtained.

scholarly journals (Y,Gd)BO3:Eu red phosphor for dual-layer phosphor structure to enhance the optical performance of white light-emitting diodes

2021 ◽  
Vol 10 (4) ◽  
pp. 1930-1935
Author(s):  
Phan Xuan Le ◽  
Le Hung Tien
Keyword(s):  
White Light ◽  
Light Emitting Diodes ◽  
Red Light ◽  
Phosphor Layer ◽  
Light Emitting ◽  
Conformal Coating ◽  
Color Quality ◽  
Remote Phosphor ◽  
White Light Emitting Diodes ◽  
Color Rendering

Among the structures using for fabricating white light-emitting diodes (WLEDs) such as the conformal coating or in-cup geometries, the remote phosphor structure gives the highest luminous efficacy. However, in terms of color quality, its performance is not as good as the others. The red-light compensation has been reported as the effective solution for enhancing the color quality of WLEDs. Hence, this study adopted the idea and applied to the dual-layer phosphor structure. The phosphor used to boost the red color in light formation is (Y,Gd)BO3:Eu particle. The dual-layer remote phosphor structure was simulated with the red (Y,Gd)BO3:Eu phosphor layer above the original yellow phosphor YAG:Ce3+ one. The WLEDs with different correlated color temperatures of 5600 K, 6600 K and 7700K were experimented. Mie-theory and Lambert-Beer law were applied to examine the results. The growth in color rendering index (CRI) and color quality scale (CQS) with the increase of (Y,Gd)BO3:Eu phosphor concentration was observed. Nevertheless, the lumen efficacy would be degraded if the concentration was over a certain number. The information provided in this article is useful for the development of high-power WLED production with greater color quality.

High Color Uniformity of White Light-Emitting Diodes Using Chip-Scaled Package

2018 ◽  
Vol 30 (11) ◽  
pp. 989-992 ◽  
Author(s):  
Zongtao Li ◽  
Yong Tang ◽  
Jiasheng Li ◽  
Canbiao Wu ◽  
Xinrui Ding ◽  
...  
Keyword(s):  
White Light ◽  
Light Emitting Diodes ◽  
Light Emitting ◽  
Color Uniformity ◽  
White Light Emitting Diodes

Angular color uniformity enhancement of white light-emitting diodes integrated with freeform lenses

2010 ◽  
Vol 35 (11) ◽  
pp. 1860 ◽  
Author(s):  
Kai Wang ◽  
Dan Wu ◽  
Fei Chen ◽  
Zongyuan Liu ◽  
Xiaobing Luo ◽  
...  
Keyword(s):  
White Light ◽  
Light Emitting Diodes ◽  
Light Emitting ◽  
Color Uniformity ◽  
White Light Emitting Diodes
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