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2 Materials Science Poland

2 2020

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Eu2+-activated strontium-barium silicate: a positive solution for improving luminous efficacy and color uniformity of white light-emitting diodes

Thi My Hanh Nguyen, That Phung Ton, Anh Nguyen Doan Quoc

Materials Science Poland

2020

Vol. 38, No. 4

594--600

In this research we have studied the lighting enhancement method by analyzing chromatic performance and luminous flux of light emitting diodes that produce white light. In order to achieve expected results, it is necessary to mix Eu2+-activated strontium-barium silicate (SrBaSiO4:Eu2+) with its phosphor compounding, which has been demonstrated to have considerable influence on lighting performance. The results showed that with the gradually increasing concentration of yellow-green-emitting SrBaSiO4:Eu2+phosphor in LEDs devices, at 8500 K, the color homogeneity and the lighting output received a great improvement. The color quality scale, on the other hand, responded negatively to the increase in SrBaSiO4:Eu2+. The impact of SrBaSiO4:Eu2+on optical properties of WLEDs was confirmed. The final step to optimize SrBaSiO4:Eu2+ usage in lighting development is to figure out a suitable amount of particles and optimize their size.

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

Anh Nguyen Doan Quoc, Ngoc Hoang Van

Materials Science Poland

2020

Vol. 38, No. 3

493--501

The 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.