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Improving color uniformity and color rending index of remote-phosphor packaging white LEDs by co-doping SiO2 and Sr2Si5N8:Eu2+ particles

Minh T. H. Q., Nhan N. H. K., Anh N. D. Q., Nam T. T., Lee H.-Y.

Materials Science Poland

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2018

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Vol. 36, No. 3

370--374

EN

Based on some advantageous properties, such as fast response time, environment friendliness, small size, long lifetime, and high efficiency, white LEDs are increasingly used in common illumination applications. In this research, by co-doping of redemitting Sr2Si5N8:Eu2+ phosphor and adding SiO2 particles to yellow-emitting YAG:Ce phosphor compounds, a new approach for improving color uniformity and color rending index of remote-phosphor structure white LEDs is proposed and demonstrated. The obtained results clearly indicate that the color rendering index (CRI) and color uniformity (DCCT) significantly depend on Sr2Si5N8:Eu2+ concentration. The results provide a potential practical solution for manufacturing remote-phosphor white LEDs (RP-WLEDs) in the near future.

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Green-emitting CaF2:Ce3+,Tb3+ phosphor: selection for improving luminous flux and color quality of conformal geometry white LED lamps

Tin P. T., Minh T. H. Q., Nhan N. H. K., Lee H.-Y., Trang T. T.

Materials Science Poland

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2018

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Vol. 36, No. 4

563--569

EN

In the last decades, new solutions for improving lighting properties of white LED lamps (WLEDs) have been the main research direction in optoelectronics. In this paper, a modern approach for enhancing luminous flux and color quality of white LED lamps was presented. By mixing green-emitting CaF2:Ce3+,Tb3+ phosphor with yellow-emitting YAG:Ce phosphor compound, the luminous flux and color quality of white LED lamps with conformal phosphor geometry (CPG) increased significantly. From the obtained results it follows that, the luminous flux increased more than 1.5 times, and the correlated color temperature deviation decreased more than 4 times in comparison with the non-green-emitting CaF2:Ce3+,Tb3+ phosphor. The presented research shows that the green-emitting CaF2:Ce3+,Tb3+ phosphor could become a good candidate for enhancing luminous flux and color quality of white LED lamps.

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

Minh T. H. Q., Nhan N. H. K., Anh N. D. Q., Lee H.-Y.

Materials Science Poland

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2017

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Vol. 35, No. 3

618--625

EN

This 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.