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2 Materials Science Poland

2 2020

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w słowach kluczowych: Mie-scattering theory

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

100%

Thi M. H. N. , That P. T. , Anh N. D. Q.

tom 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.

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

86%

Thi M. H. N. , That P. T. , Anh N. D. Q. , Thanh T. T.

tom Vol. 38, No. 4

654--660

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.