• International Journal of Technology (IJTech)
  • Vol 13, No 4 (2022)

Selection of Multi-layer Remote Phosphor Structure for Heightened Chromaticity as well as Lumen Performance within WLED Devices

Selection of Multi-layer Remote Phosphor Structure for Heightened Chromaticity as well as Lumen Performance within WLED Devices

Title: Selection of Multi-layer Remote Phosphor Structure for Heightened Chromaticity as well as Lumen Performance within WLED Devices
Phuc Dang Huu, Dieu An Nguyen Thi

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Published at : 07 Oct 2022
Volume : IJtech Vol 13, No 4 (2022)
DOI : https://doi.org/10.14716/ijtech.v13i4.5051

Cite this article as:
Huu, P.D., Thi, D.A.N., 2022. Selection of Multi-layer Remote Phosphor Structure for Heightened Chromaticity and Luminous Performance of White Light-emitting Diodes. International Journal of Technology. Volume 13(4), pp. 837-847

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Phuc Dang Huu Institute of Applied Technology, Thu Dau Mot University, Binh Duong Province, Vietnam
Dieu An Nguyen Thi Faculty of Electrical Engineering Technology, Industrial University of Ho Chi Minh City, Ho Chi Minh City, Vietnam
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Abstract
Selection of Multi-layer Remote Phosphor Structure for Heightened Chromaticity as well as Lumen Performance within WLED Devices

The hue output for remote phosphor layout is still a concern for researchers and producers working on developing WLED devices since said layout proves inferior to the conformal or in-cup phosphor package. However, the luminous efficiency in the layout showed significant improvements. Thus, this study aims to achieve higher color quality accompanied by high lumen output for remote phosphor structures by using additional phosphor layers. Specifically, the study introduces the double-film and triple-film configurations in which the red and green phosphors were added. The best structure for WLED applications is determined by comparing these structures. The influences of each phosphor structure are investigated and examined on optical parameters of WLEDs, which have different correlated hue temperatures between 5600 K and 8500 K. The optical features are CRI, CQS, color deviation (CD), and photoluminescence (PL). The results demonstrate that the triple-layer structure improved the color quality more effectively than the dual-layer structure due to higher attained CRI and CQS and smaller DC figures. The hypothesis of Mie-scattering indicates that the enhancement of scattering in the triple-layer is responsible for these achievements. Thus, the findings of this study are reliable and valuable for manufacturers.

Color quality; Color quality scale; Color rendering index; Luminous efficiency; Remote phosphor structure; Triple-layer phosphor structure; WLEDs

Introduction

    Light-emitting diodes (LEDs) have laid the concrete foundation for their widespread usage in the solid-state lighting (SSL) industry (Sulistiyanto et al., 2014; Widiyati et al., 2018). They can especially be served as an alternative solution to halogen, incandescent, and fluorescent illuminating systems since they are safer and sturdier. Researchers also pointed out that LEDs potentially have better energy conversion efficiency leading to less heat release, longer lifetime, and more stable brightness performance (Nguyen et al., 2021a; Luo et al., 2020). A LED package was conventionally fabricated utilizing the synthetic of a blue chip and a yellow phosphor material. Thus, the generated light of LED was comprised of blue and yellow lights from these two elements (Anh et al., 2017b). The freely dispersed phosphor coating is one of the most simple and massively applied techniques for manufacturing WLEDs. The mixture of phosphor particles and silicone was spread freely above the bare blue chip.

The advantages of using said method were adjustable phosphor layer thickness and low cost, yet the disadvantage is the poor optical performance of the LED package. Therefore, it is inappropriate to produce high-power WLEDs (Jiang et al., 2017; Yang et al., 2019b; Yuce et al., 2019). The conformal phosphor coating was then introduced to improve the quality of LEDs. Even though this method effectively enhanced the color uniformity due to its ability to provide uniform color distribution, the backscattering in the package caused degradation in light extraction efficiency (Yang et al., 2019a; Ding et al., 2018; Gao et al., 2018). Additionally, these methods directly placed the phosphor layer onto the LED chip surface, stimulating calefaction at the joint and reducing the phosphor's efficiency and the lifetime of the LED device. Hence, researchers devised the idea of creating a gap or adding another film between the main phosphor-silicone encapsulation and the LED chip to improve light extraction and minimize heat generation (Anh et al., 2020; Zhang et al., 2016). This structure was called the remote phosphor structure, and it fastly became a popular topic in various studies of enhancements for WLEDs’ optical properties. A thermal-isolated encapsulation was designed to increase the light output power by controlling heat generation during the high operation time of a WLED (Li et al., 2016). The light extraction efficiency of the remote phosphor package was improved using various approaches, including internal reflection enhancement by employing the innerphosphor-coated polymer hemispherical shell lens, downward-light reflection by the airgap embedded structure, and backscattered-light reduction by the ring remote phosphor structure (Ge et al., 2015). To create a high-grade WLED, aside from the essential light extraction efficiency, another decisive factor is color quality, including CRI and CQS. The study introduced the layout with two sheets to improve chromatic adequacy and luminous efficiency. It was shown that by using the remote phosphor structure with two phosphor layers, the WLED package could improve its lumen output by 5% and color uniformity by offering a significant reduction in the angular color deviation (Thon et al., 2021). However, the performance of a dual-layer phosphor package is usually determined by the phosphor layer that has been added. Notably, with a red phosphor layer, CRI figures can be improved, but the luminous flux is degraded, and vice versa in the case of using green phosphor. Besides, according to previous studies, the growth in phosphor concentration led to a higher reabsorption loss in the package, which decreased the luminous flux (Cheng et al., 2019; Anh et al., 2017a). Then, the concept of using one more phosphor layer can be potential consideration. The triple-film distant phosphor configuration was proposed with the participation of the yellow, green, and red phosphor films. The first film is the yellow phosphor, which is closest to the LED chip, the second film is the green phosphor, and the third film is the red phosphor. In this study, the authors concentrate on the performance of triple-layer remote phosphor film on the illumination effectiveness of the WLED. Phosphor concentrations are also adjusted to observe and analyze changes in the packages of light extraction, emission spectra, color deviation, CRI, and CQS (Davis & Ohno, 2010). Furthermore, the comparison among the single-layer, two-sheet, and three-sheet remote layouts is presented to prove that using the three-film remote design is more beneficial to the quality of LED. The phosphors used to fabricate the phosphor packages in the article are yellow phosphor YAG: Ce3+, red phosphor CaO: Eu3+, and green phosphor Zn2SiO4:Mn2+. In addition, the authors apply the hypothesis of Mie scattering and the law of Lambert-Beer to the measurements. Thus, the outcomes in this study are more reliable and can assist manufacturers in determining the most suitable remote phosphor package to accomplish their goals in high-power WLED production.


Conclusion

The comparison of lighting performance among the triple-layer (YGR), dual-layer (YG and YR), and single-layer (Y) are provided in this article to figure out the most suitable remote phosphor structure for further WLED developments. WLED models are simulated using green Zn2SiO4:Mn2+ and red CaO:Eu3+. Mie's hypothesis and Beer's law would be utilized to investigate and validate the measured outcomes. The findings indicate that the YR is advantageous to the CRI of the WLED as the red phosphor helps to increase the red components in the white-light spectral region. At the same time, the YG is suitable for the luminous flux due to the rise in the green spectral intensity. Despite ranking second in terms of CRI, the YGR has the highest value in CQS and luminous efficacy regardless of CCTs. Moreover, the color deviation in YGR is the smallest, implying that the color uniformity in YGR is the highest. Therefore, YGR is the superior remote structure that can be used for higher quality WLED creation.

Acknowledgement

This research is supported by the Industrial University of Ho Chi Minh City (IUH) under grant number 121/HD-DHCN.

References

Agarwal, S., Haseman, M.S., Khamehchi, A., Saadatkia, P., Winarski, D.J., Selim, F.A., 2017. The Physical and Optical Properties of Ce: YAG Nanophosphors and Transparent Ceramics and the Observation of Novel Luminescence Phenomenon. Optical Materials Express, Volume 7, pp. 1055–1065

Anh, N.D.Q., Vinh, N.H., Lee, H.Y., 2017a. Effect of Red-emitting Sr2.41F2.59B20.03O74.8:Eu0.12, Sm0.048 Phosphor on Color Rendering Index and Luminous Efficacy of White LEDs.  Current Optics and Photonics, Volume 1(2), pp. 118–124

Anh, N.D.Q., Vinh, N.H., Lee, H.Y., 2017b. Gaussian Decomposition Method in Designing a Freeform Lens for an LED Fishing/Working Lamp. Current Optics and Photonics, Volume 1(3), pp. 233–238

Anh, N.D.Q., Ngoc, H.V., 2020. Building Superior Lighting Properties for Wleds Utilizing Two-Layered Remote Phosphor Configurations. Materials Science-Poland, Volume 38, pp. 493–501

Cheng, J., Zhang, J., Lu, J., Bian, X.T., Zhang, H.C., Shen, Z.H., Ni, X.W., Ma, P.C., Shi, J., 2019. Photoluminescence Properties of Ca4La6(SiO4)4(PO4)2O2-Based Phosphors for wLEDs. Chinese Optics Letters, Volume 17(5), p. 051602

Davis, W., Ohno, Y., 2010. Color Quality Scale. Optical Engineering, Volume 49(3), p. 033602

Ding, X.R., Chen, Q., Tang, Y., Li, J.S., Talwar, D.P., Yu, B.H., Li, Z.T. 2018. Improving the Optical Performance of Multi-Chip LEDs by using Patterned Phosphor Configurations. Optics Express, Volume 26(6), pp. A283–A292

Gao, W.J., Ding, K., He, G.X., Zhong, P., 2018. Color Temperature Tunable Phosphor-Coated White LEDs with Excellent Photometric and Colorimetric Performances. Applied Optics, Volume 57, pp. 9322–9327

Ge, Z., Piquette, A., Mishra, K.C., Klotzkin, D., 2015. Enhanced Forward Emission of YAG: Ce3+ Phosphor with Polystyrene Nanosphere Coating. Applied Optics, Volume 54, pp. 6025–6028

Irawan, Y., Juliana, I., Adilina, I.B., Alli, Y.F., 2017. Aqueous Stability Studies of Polyethylene Glycol and Oleic Acid-Based Anionic Surfactants for Application in Enhanced Oil Recovery through Dynamic Light Scattering. International Journal of Technology. Volume 8(8), pp. 1414–1421

Jiang, P.Q., Peng, Y., Mou, Y., Cheng, H., Chen, M.X., Liu, S., 2017. Thermally Stable Multicolor Phosphor-In-Glass Bonded on Flip-Chip UV-LEDs for Chromaticity-Tunable WLEDs. Applied Optics, Volume 56, pp. 7921–7926

Li, B., Zhang, D.W., Huang, Y., Ni, Z., Zhuang, S., 2010. A New Structure of Multi-Layer Phosphor Package of White LED with High Efficiency. Chinese Optics Letters, Volume 8(2), pp. 221–223

Li, J.S., Chen, Y.H., Li, Z.T., Yu, S.D., Tang, Y., Ding, X.R., Yuan, W. 2016. ACU Optimization of pcLEDs by Combining the Pulsed Spray and Feedback Method. Journal Display of Technology, Volume 12(10), pp. 1229–1234

Liu, Z., Liu, S., Wang, K., Luo, X., 2010. Measurement and Numerical Studies of Optical Properties of YAG: Ce Phosphor for White Light-Emitting Diode Packaging. Applied Optics, Volume 49(2), pp. 247–257

Luo, G.F., Loan, N.T.P., Tho, L.V., Anh, N.D.Q., Lee, H.Y., 2020. Enhancement Of Color Quality and Luminous Flux for Remote-Phosphor Leds with Red-Emitting CaMgSi2O6:Eu2+, Mn2+. Materials Science-Poland, Volume 38, pp. 409–415

Nguyen, T.M.H., Ton, T.P., Anh, N.D.Q., 2021a. Eu-Activated Strontium-Barium Silicate: A Positive Solution for Improving Luminous Efficacy and Color Uniformity of White Light-Emitting Diodes. Materials Science-Poland, Volume 38, pp. 594–600

Nguyen, T.M.H., Ton, T.P., Anh, N.D.Q., Thanh T.T., 2021b. Triple-layer remote phosphor structure: a novel option for enhancing WLEDs’ color quality and luminous flux" Materials Science-Poland, Volume 38(3), pp. 654–660

Sulistiyanto, N., Rifan, M., Setyawati, O., 2014. Development of a 20V-LED Driver Based on the Boost Converter using an FPGA Module. International Journal of Technology, Volume 5(3), pp.287–292

Ton, T.P., Phuong, L.N.T., Le, V.T., Anh, N.D.Q., Liao, H.Y., Luo, G.F., Lee, H.Y., 2021. Enhancing Color Quality of WLEDs with Dual-Layer Remote Phosphor Geometry. Materials Science- Poland, 38(4), pp. 667–674

Widiyati, C., Poernomo, H., 2018. Design of a Prototype Photoreactor UV-LEDs for Radiation Vulcanization of Natural Rubber Latex. International Journal of Technology. Volume 9(1), pp. 130–141

Yang, L., Zhang, Q., Li, F., Xie, A., Mao, L., Ma, J.D. 2019a. Thermally Stable Lead-Free Phosphor in Glass Enhancement Performance of Light Emitting Diodes Application. Applied Optics, Volume 58(15), pp. 4099–4104

Yang, X., Chai, C.F., Chen, J.C., Zheng S.S., Chen, C., 2019b. Single 395 nm Excitation Warm WLED with a Luminous Efficiency of 104.86 lm/W and a Color Rendering Index of 90.7. Optical Materials Express, Volume 9(11), pp. 4273–4286

Yuce, H., Guner, T., Balci, S., Demir, M.M., 2019. Phosphor-Based White LED by Various Glassy Particles: Control Over Luminous Efficiency. Optics Letters, Volume 44(3), pp. 479–482

Zhang, J., Ji, B.W., Hua, Z.H., 2016. Investigations on the Luminescence of Ba2Mg(PO4)2:Eu2+, Mn2+ Phosphors for LEDs. Optical Materials Express, Volume 6(11), pp. 3470–3475

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Table of Contents
Article
Abstract
Introduction
Conclusion
Acknowlegement
References