scholarly journals Dual-layer remote phosphor structure: a novel technique to enhance the color quality scale and luminous flux of WLEDs

2020 ◽  
Vol 10 (4) ◽  
pp. 4015
Author(s):  
Phung Ton That ◽  
Thuc Minh Bui ◽  
Nguyen Thi Phuong Loan ◽  
Phan Xuan Le ◽  
Nguyen Doan Quoc Anh ◽  
...  
Keyword(s):  
Red Light ◽  
Single Layer ◽  
Luminous Flux ◽  
Phosphor Layer ◽  
Red Phosphor ◽  
Light Emitting ◽  
Color Quality ◽  
Quality Scale ◽  
Remote Phosphor ◽  
The Right

The effects of red light-emitting phosphor CaMgSi2O6:Eu2+,Mn2+ on the optical properties of single-layer remote phosphor structure (SRPS) and dual-layer remote phosphor structure (DRPS) are the focus of this study. The differences in color quality and luminous flux (LF) of white light-emitting diodes (WLEDs) between these two structures are also revealed and demonstrated based on the Mie theory. SRPS consists of one mixed phosphor layer betweenCaMgSi2O6:Eu2+,Mn2+ andYAG:Ce3+particles, while DRPS includes two separated layers: red phosphor layer and yellow phosphor layer. In this work, 5% SiO2 is added into the phosphor layers to increase scattering abilities. Discrepancies in structures greatly affect the optical characteristics of WLEDs. The results showed that the color rendering index (CRI) increased with the concentration in both structures with nearly equal values. Meanwhile, color quality scale (CQS) of DPRS is 74 at ACCTs ranging from 5600K to 8500K, higher than CQS of SRPS which is only 71 at 8500K. In addition, the luminous flux of DRPS is significantly higher than SRPS at 2% -14% of CaMgSi2O6:Eu2+,Mn2+. In summary, DRPS is better for color quality and lumen outputin comparison to SRPS and adding the right amount of red phosphor can enhance CQS and LF.

scholarly journals The Application of Mg2TiO4:Mn4+ and NaYF4:Er3+;Yb3+ and Double Convex Structure in Improving Optical Performance of Phosphor-in-Glass Based White Light-Emitting Diodes

2020 ◽  
Vol 4 (4) ◽  
pp. 218
Author(s):  
Thinh Cong Tran ◽  
Guo-Feng Luo ◽  
Thi Phuong Loan Nguyen ◽  
Van Tho Le ◽  
Doan Quoc Anh Nguyen
Keyword(s):  
Mie Scattering ◽  
Luminous Flux ◽  
Phosphor Layer ◽  
Green Phosphor ◽  
Red Phosphor ◽  
Light Emitting ◽  
Creative Commons ◽  
Color Quality ◽  
Remote Phosphor ◽  
Manufacturing Procedure

Improving lighting performance of WLEDs, especially the color quality, has always been a priority in lighting researches. Recently, the conventional remote phosphor configuration is unable to fulfill the needs of the modern lighting market, particularly the high color expression demand has inspired the search for a novel manufacturing procedure. In this study, based on the results from previous studies, the struggles in enhancing lighting performances are pointed out, and a solution, the dual-layer remote phosphor, is proposed from our conducted experiments. Through experiments with NaYF4:Er3+;Yb3+ and Mg2TiO4:Mn4+ phosphors, the dual-layer phosphor is proven to be effective in improving lighting properties such as color rendering index (CRI) and color quality scale (CQS). The research method involves structuring and experimenting with the phosphor configuration of the yellow phosphor YAG:Ce3+ layer with a green NaYF4:Er3+;Yb3+ or a red Mg2TiO4:Mn4+ phosphor layer whose phosphor concentrations are varied. The results show that the red phosphor Mg2TiO4:Mn4+ particles benefit the CRI and CQS because the values of CRI and CQS increase with red phosphor Mg2TiO4:Mn4+ concentration. On the other hand, the green phosphor NaYF4:Er3+;Yb3+ is inferior in improving CRI and CQS but exhibits better luminous flux. Despite being useful in enhancing lighting performance, the phosphor concentration must be kept below a certain level, which will be mentioned in the article, to prevent damages. These results are verified using Mie scattering theory and Lambert-Beer's law and can be utilized in producing WLEDs with high lighting quality. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

scholarly journals Building superior lighting properties for WLEDs utilizing two-layered remote phosphor configurations

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Guo-Feng Luo ◽  
Nguyen Thi Phuong Loan ◽  
Le Van Tho ◽  
Phung Ton That ◽  
Nguyen Doan Quoc Anh ◽  
...  
Keyword(s):  
Red Light ◽  
Mie Scattering ◽  
Luminous Flux ◽  
Color Temperature ◽  
Phosphor Layer ◽  
Green Phosphor ◽  
Red Phosphor ◽  
Color Quality ◽  
Remote Phosphor ◽  
Chromatic Properties

AbstractThe remote phosphor structure produces higher luminous flux but delivers poorer color quality than the conformal or in-cup phosphor structure. To eliminate this weakness, researchers have attempted to improve the chromatic properties of remote phosphor package. This study tends to enhance lighting features for WLEDs including color quality and luminous flux in general or color rendering index (CRI) and color quality scale (CQS) in particular by applying dual-layer remote phosphor structure. In the simulation section, we utilize two identical LEDs that only differ in correlated color temperature values which are 6600 K and 7700 K. The study offers an idea of placing a yellow-green phosphor layer SrBaSiO4:Eu2+ or a red phosphor layer SrwFxByOz:Eu2+,Sm2+ on the yellow phosphor layer YAG:Ce3+ and then modifying the concentrations of SrwFxByOz:Eu2+,Sm2+ and SrBaSiO4:Eu2+ to the suitable values to improve the color quality and lumen output of WLEDs. The results show that red phosphor layer SrwFxByOz:Eu2+,Sm2+ has a significant influence on CRI and CQS improvement. Particularly, the increase of SrwFxByOz:Eu2+,Sm2+ concentration leads to increased CRI and CQS because the red light component increases in WLEDs. On the other hand, the green phosphor layer SrBaSiO4:Eu2+ only brings benefit to the luminous flux. However, the WLEDs’ luminous flux and color quality drop sharply, when SrwFxByOz:Eu2+,Sm2+ and SrBaSiO4:Eu2+ concentrations rise extremely, which is verified based on the Mie-scattering theory and the Lambert-Beer law. In short, the article provides general knowledge and primary information for the production of higher-quality WLEDs.

scholarly journals The application of double-layer remote phosphor structures in increasing WLEDs color rendering index and lumen output

2020 ◽  
Vol 10 (5) ◽  
pp. 5183
Author(s):  
Nguyen Thi Phuong Loan ◽  
Nguyen Doan Quoc Anh
Keyword(s):  
Red Light ◽  
Mie Scattering ◽  
Luminous Flux ◽  
Color Temperature ◽  
Phosphor Layer ◽  
Green Phosphor ◽  
Red Phosphor ◽  
Color Quality ◽  
Remote Phosphor ◽  
Different Color

The remote phosphor structure often has inferior color quality but better luminous flux in than conformal or in-cup configurations. Therefore, numerous researches study remote phosphor structure for methods to enhance it chromatic quality. This study introduces the use of dual-layer remote phosphor structure in WLEDs with identical structure but at different color temperature, 6600K and 7700K, to demonstrate their effect on quality indicators. The concept is placing a green phosphor layer (Ce,Tb)MgAl11O19:Ce:Tb or a red phosphor layer MgSr3Si2O8:Eu2+,Mn2+ on the layer of yellow-emitting phosphor YAG:Ce3+ and find the suitable concentration of the additional phosphor to create the best color quality. The results showed that the increase of CRI and CQS are affected by MgSr3Si2O8:Eu2+,Mn2+, in particular, the higher the concentration of red phosphor gets the better CRI and CQS because the emitted red light in enhanced. The green phosphor layer (Ce,Tb)MgAl11O19:Ce:Tb, on the other hand, is beneficial for the luminous flux. The concentration of MgSr3Si2O8:Eu2+,Mn2+ and (Ce,Tb)MgAl11O19:Ce:Tb, however, need to be adjusted properly to avoid decreasing the luminous flux due to overgrowth. The Mie scattering theory and Beer’s law are the verification tools for these conclusions, which gives them the credibility to be applied in producing better quality WLEDs.

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.

scholarly journals The Impacts of Red-emitting Mg2TiO4:Mn4+ Phosphor on Color Quality of Dual-layer Remote Phosphor Configuration

2019 ◽  
Vol 3 (3) ◽  
pp. 464
Author(s):  
Hsiao-Yi Lee ◽  
Phan Xuan Le ◽  
Doan Quoc Anh Nguyen
Keyword(s):  
Red Light ◽  
Mie Scattering ◽  
Conformal Structure ◽  
Luminous Flux ◽  
Color Temperature ◽  
Phosphor Layer ◽  
Creative Commons ◽  
Color Quality ◽  
Remote Phosphor ◽  
Color Rendering

In terms of luminous flux, the remote phosphor structure is better than conformal structure or in-cup phosphor structure, however, this structure often has inferior color quality compared to the others. As a result, many studies have been conducted to nd a solution to the drawback mentioned above. In this research, we are after the same goal using WLEDs structure with color temperature of 5600 K and come to the conclusion that dual-layer phosphor structure can improve the color rendering index (CRI) and the color quality scale (CQS). The concept of the research is to place red phosphor layer Mg2TiO4:Mn4+ on a yellow phosphor layer YAG:Ce3+ and locate the concentration of Mg2TiO4:Mn4+ that allows the color quality to reach the highest value. The result shows that Mg2TiO4:Mn4+ benets CRI and CQS, more specifically, the addition of Mg2TiO4:Mn4+ in WLEDs boosts the red light component, thus, enhancing CRI and CQS. However, it is demonstrated through the application of Mie-scattering theory and Lambert-Beer law that when the concentration of Mg2TiO4:Mn4+ exceed the limit, it can harm the luminous flux of WLEDs. The result of this research is a valuable contribution to improving the techniques of manufacturing better WLEDs with higher white light quality.  This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

scholarly journals Improvement of double-layer phosphor structure WLEDS in color homogeneity and luminous flux

2021 ◽  
Vol 10 (5) ◽  
pp. 2513-2519
Author(s):  
Dieu An Nguyen Thi ◽  
Phung Ton That ◽  
Hoang Nam Nguyen
Keyword(s):  
Luminous Flux ◽  
Small Reduction ◽  
Phosphor Layer ◽  
Green Phosphor ◽  
Yellow Phosphor ◽  
Color Quality ◽  
Quality Scale ◽  
Remote Phosphor ◽  
Distinct Color ◽  
Color Rendering

The concept of the analysis is to put a CaAl2O4:Mn2+ green phosphor layer on top of the YAG:Ce3+ yellow phosphor layer. After that, find the added CaAl2O4:Mn2+ concentration appropriate for the highest luminous flux (LF) and color homogeneity (CH). In this analysis, five equivalent WLEDs were applied but with distinct color temperatures, including 5600 K - 8500 K. The findings showed that CaAl2O4:Mn2+ brings great benefits to increase not only the luminous flux but also the color homogeneity. Especially, the higher the CaAl2O4:Mn2+ concentration, the more the luminous flux released by WLEDs, owing to the risen content of the light of green in WLEDs. Nevertheless, as the CaAl2O4:Mn2+ concentration raised significantly, a small reduction in the color rendering metric (CRI) and color quality scale (CQS) occurred. This is supported by simulation and calculation according to the theory of Monte Carlo. The paper results are the crucial contribution to the manufacture of WLEDs with better optical performance and color homogeneity of remote phosphor configurations.

scholarly journals Triple-layer remote phosphor structure: a novel option for the enhancement of WLEDs’ color quality and luminous flux

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
My Hanh Nguyen Thi ◽  
Phung Ton That ◽  
Nguyen Doan Quoc Anh ◽  
Tran Thanh Trang
Keyword(s):  
Performance Enhancement ◽  
Light Output ◽  
Luminous Flux ◽  
White Leds ◽  
Color Quality ◽  
Quality Scale ◽  
Color Uniformity ◽  
Remote Phosphor ◽  
Research Findings ◽  
Color Rendering

Abstract The remote phosphor as a lighting structure has outstanding luminous efficiency compared to other options, such as conformal or in-cup. However, the lack of uniformity in distributed color has prevented remote phosphor from wider development. The answer to the chromatic performance enhancement that has been suggested by numerous researchers is the multi-layer configuration with two or three different types of chromatic phosphor. The research purpose is to select the best configuration for multi-chip white LEDs (WLEDs) to achieve optimal results in color quality scale (CQS), color rendering index (CRI), light output and color homogeneity. WLEDs mentioned in this paper have two distinct color temperatures, 6600 K and 7700 K. Experimental results show that the remote phosphor structure with three phosphor layers is superior in terms of color rendering, chromatic performance, and emitted light. The deviation of correlated color measured in this structure is also low, which means that the color uniformity is greatly enhanced in this multi-layer lighting structure. This result can be demonstrated by analyzing the scattering characteristics of the phosphoric layers using the Mie theory. The research findings have proven the effectiveness of the multi-phosphor configuration and can serve as a guideline to fabricate WLEDs with better performance.

scholarly journals Enhancing color quality of WLEDs with dual-layer remote phosphor geometry

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Phung Ton That ◽  
Nguyen Thi Phuong Loan ◽  
Le Van Tho ◽  
Nguyen Doan Quoc Anh ◽  
Hsing-Yuan Liao ◽  
...  
Keyword(s):  
Red Light ◽  
Mie Scattering ◽  
Phosphor Layer ◽  
Color Quality ◽  
Remote Phosphor ◽  
Different Color ◽  
Light Components ◽  
Two Parameters ◽  
Color Rendering

Abstract Usually, remote phosphor structures are beneficial in terms of flux but unfavorable in terms of color quality compared to conformal phosphor or in-cup phosphor packages. To eliminate this disadvantage, many studies have focused on increasing the chromatic quality of the remote phosphor configuration, which requires great efforts in improving two parameters of color: color rendering index (CRI) and color quality scale (CQS). CRI is known as the most useful quantitative method used to measure the ability of a light source to reproduce the colors of illuminated objects faithfully and naturally. Similarly, CQS is also a method of lighting quality determination and analysis, especially used as an alternative to the unsaturated CRI colors. In this paper, we proposed dual-layer remote phosphor structure as a novel method of CRI and CQS enhancement to improve WLEDs’ color quality. Five alike WLEDs but having different color temperatures in the range of 5600 K to 8500 K were applied in this study. The idea behind the study is to place a red phosphor layer SrwFxByOz:Eu2+,Sm2+ on the yellow phosphor layer YAG:Ce3+ and then determining an appropriate concentration of SrwFxByOz:Eu2+,Sm2+ added to achieve the highest color quality. The results point out that SrwFxByOz:Eu2+,Sm2+ brings great benefits to the improvement of CRI and CQS parameters. Specifically, the higher the SrwFxByOz:Eu2+,Sm2+ concentration results in the greater CRI and CQS, owning to the enriched red light components in the WLEDs. However, the flux has a tendency of dropping when SrwFxByOz:Eu2+,Sm2+ concentration rises excessively. This has been proved by using the Mie-scattering theory and the Lambert-Beer law. The results of this article are essential references for manufacturing WLEDs with higher chromatic quality.

scholarly journals Exellent Color Quality and Luminous Flux of Wleds Using Triple-Layer Remote Phosphor Configuration

2020 ◽  
Vol 4 (1) ◽  
pp. 74
Author(s):  
Min-Feng Lai ◽  
Hsiao-Yi Lee ◽  
Doan Quoc Anh Nguyen
Keyword(s):  
Red Light ◽  
Green Light ◽  
Luminous Flux ◽  
Green Phosphor ◽  
Light Component ◽  
Research Results ◽  
White Leds ◽  
Color Quality ◽  
Triple Layer ◽  
Remote Phosphor

This study proposed a triple-layer remote phosphor (TRP) structure to improve the color and luminous flux of white LEDs (WLEDs). TRP structure consists of 3 different phosphor layers: yellow YAG:Ce3+ layer below, red CaMgSi2O6:Eu2+,Mn2+ phosphor on top and green layer Ba2Li2Si2O7:Sn2+,Mn2+  phosphor in the middle. Using red CaMgSi2O6:Eu2+,Mn2+ to control the red light component leads to increased color rendering index (CRI). Utilize the green CaMgSi2O6:Eu2+,Mn2+ phosphor to control the green light component results in the increase in luminous efficacy (LE) of WLEDs. Furthermore, when the concentration of these two phosphors increased, yellow layer concentration YAG:Ce3+ decreased to maintain average correlated color temperatures (ACCTs) in the range from 6000 K-8500K. Besides CRI and LE, color quality scale (CQS) is also analyzed through concentration control of green phosphor and red phosphor. The research results show that the higher the concentration of CaMgSi2O6:Eu2+,Mn2+, the better for CRI. In contrast, CRI decreased significantly when increasing the concentration of Ba2Li2Si2O7:Sn2+,Mn2+. Meanwhile, CQS achieve notable enhancement in the concentration range of 10% -14% CaMgSi2O6:Eu2+,Mn2+, regardless of Ba2Li2Si2O7:Sn2+,Mn2+ concentration. LE, in particular, can also increase by more than 40% along with the improvement of CRI and CQS with the reduction of the backscattered light and addition of green light. Research results are a valuable reference for producers who wish to improve the color quality and enhance the luminous flux of WLEDs. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

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