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A novel phosphor structure for improving the luminous flux of white LEDs Nguyen Thi Phuong Thao; Jan Nedoma; Le Anh Vu; Dieu An Nguyen Thi
Bulletin of Electrical Engineering and Informatics Vol 11, No 2: April 2022
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/eei.v11i2.3608

This section focuses on the color uniformity and luminous production of multi-chip white-emitted LED lighting systems (MCW-LEDs) in improving illuminated performance. To accomplish the desired outcome, CaO:Sb3+ must be mixed with their phosphor compounding, which has been shown to have a massive impact on illuminating effectiveness. There is also evidence that the increasing of yellowish-green-emitted phosphorus CaO:Sb3+ concentration supports color homogeneity as well as luminescent effectiveness enhancements in MCW-LEDs featuring a 8500 K correlating colour temperature (CCT). Meanwhile, that rise in CaO:Sb3+ concentration leads to the gradually deteriorating color quality scale. Thus, if appropriate concentration and particle size of CaO:Sb3+ phosphor are determined, it is not hard to obtain such an excellent presentation in color uniformity, color quality scale and luminescence of MCW-LEDs.

Improvement of double-layer phosphor structure WLEDS in color homogeneity and luminous flux Dieu An Nguyen Thi; Phung Ton That; Hoang Nam Nguyen
Bulletin of Electrical Engineering and Informatics Vol 10, No 5: October 2021
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/eei.v10i5.2914

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.

Two-layer remote phosphor package as a solution to promote color quality scale and lumen in WLEDs Phuc Dang Huu; Dieu An Nguyen Thi
Bulletin of Electrical Engineering and Informatics Vol 11, No 3: June 2022
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/eei.v11i3.3766

This article demonstrates the influence of the red-light LaAsO4:Eu3+ phosphorus on the optical features of the two structures: one-layer remote phosphorus scheme (SRPS) and two-layer remote phosphorus scheme (DRPS). As a result, the Mie hypothesis is used to demonstrate and prove the comparison between color quality and luminosity (LF) between these two factors. The SRPS is a phosphor layer that consists of LaAsO4:Eu3+ particles combined with the YAG:Ce3+ mixture. Meanwhile, DRPS is two phosphor layers of red and yellow separated from each other. To improve the dispersing property, 5% of SiO2 is combined with the phosphorous films. The difference between the structures influences the optical features of WLEDs. The obtained outcomes show that the color rendering index (CRI) rises along with the concentrations of both structures while these values are nearly identical to each other. Meanwhile, at ACCTs (5600 K - 8500 K), the color quality scale (CQS) in DRPS reaches 74, which is higher than SRPS's 71 at 8500 K. Besides, the lumen in DRPS is considerably greater than that in SRPS at 2%-14% LaAsO4:Eu3+. In short, DRPS brings considerable benefits to the color quality and lumen when compared to SRPS. In addition, choosing a suitable concentration also becomes highly vital to achieve desirable CQS and LF.

Using liquid phase precursor method to create a high-efficiency Ca2SiO4:Eu2+ green-emitting phosphor Phuc Dang Huu; Dieu An Nguyen Thi
Bulletin of Electrical Engineering and Informatics Vol 11, No 3: June 2022
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/eei.v11i3.3767

A standard solid-state reaction (SSR), a new fluid phase preparatory method utilizing LPP-SiO2(sol), and a water-based soluble silicone compound were employed to manufacture green Eu2+-based Ca2SiO4 phosphors liquid phase precursor (LPP-WSS). The generated phosphors feature large excitation spectra in the range of 225–450 nm and a strong green emission reaches the peak value at 502 nm owing to a 4f65d1→4f7(8S7/2) transition of Eu2+. These samples burned at 1100 1C produce the highest luminous intensity. The luminous properties of phosphors, which are manufactured by the liquid phase precursor LPP-WSS technique, were investigated at the range of 0.1-5.0 mol percent of Eu2+, with the maximum emission density observed at the value of 3.0 mol percent of Eu2+. The phosphors produced by the LPP-WSS technique exhibited a more uniform phase dispersion and higher luminous strength than those produced using the other procedures, according to a detailed report based on numerous characterizations. As a result, Ca2SiO4:Eu2+ has an indisputable possibility in white light-emitting diodes WLEDs and fluorescent lighting.

Application of green-emitting ZnS:Eu2+ for boosting the spectrum of white light-emitting diode packages Dieu An Nguyen Thi; Phuc Dang Huu
International Journal of Electrical and Computer Engineering (IJECE) Vol 12, No 5: October 2022
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijece.v12i5.pp4765-4771

Through utilizing a nonlinear application to acquire the best lumen efficiency (LE) for radiation (also known as LER) when color rendering index (CRI) value, especially CRI of R9 for strong red exceeds 90 with correlated color temperature (CCT) range of 2700-6500 K, the white light emitting diodes (WLED) package with adjustable CCT value and comprised of mixed-type light-emitting diodes (LEDs) can be acquired. The WLED model here contains blue and red LEDs with direct emission and a phosphorconversion blue LED or pc/B-LED (including orange and green phosphors mixed with blue LED colorant). The peak wavelengths of each LED constituent are 465 and 628 nm for LEDs in blue and red, 452 nm for the blue LED colorant, 530 and 586 nm for the phosphors exhibiting green and orange colors. Under the CCT of 2722-6464 K, the attained actual LED package, either with conversion phosphor, in red or in blue, possibly displays both CRI and R9 values measured from 90 to 96, color quality scale (CQS) values measured from 89 to 94, with LERs and LEs of 303-358 lm/W and 105-119 lm/W, respectively.

Quantum dot phosphors CaS:Ce3+ and CaS:Pb2+, Mn2+ for improvements of white light-emitting diodes optic characteristics Dieu An Nguyen Thi; My Hanh Nguyen Thi; Phuc Dang Huu
International Journal of Electrical and Computer Engineering (IJECE) Vol 12, No 5: October 2022
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijece.v12i5.pp4782-4789

The goal of this study is to discover a new method that uses standard phosphors and quantum dots to improve the lighting qualities and heat manipulation of white light-emitting diodes (WLEDs). Despite the popularity as a good ingredient that offers good color rendering properties, quantum dots (QDs) have not been widely employed in the fabrication of WLEDs, particularly, the utilization of QDs-phosphor-mixed nanocomposite is limited. We propose a unique packaging design based on the research’s experimental findings. The layer of nanocomposites consisting of QDs and phosphors is horizontally positioned to the WLED for optimal lighting and heating efficiency. This study simulated and used four distinguishing white LEDs forms: mono-layer phosphorus, two double-layer remote phosphors featuring yellowish-red and yellowish-green organizations, and a triple-layer phosphor. In terms of color rendering and luminous outputs, the triple-layer phosphor configuration outperforms the other implementations, as per the finding.

The impacts of (Ba,Sr)3BP3O12:Eu2+ on the luminous flux of phosphor-converted-white light emitting diode packages Van Liem Bui; Dieu An Nguyen Thi
Indonesian Journal of Electrical Engineering and Computer Science Vol 27, No 2: August 2022
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijeecs.v27.i2.pp685-691

The use of (Ba,Sr)3BP3O12:Eu2+ in the remote phosphor structure has been proposed and analysed to offer significant improvement to the lighting performance of the phosphor-converted white light emitting diode (LED). The phosphor emits green and blue spectra centred at 520 nm and 465 nm, respectively. Thus, the phosphor can compensate the blue and green light energy components in the white-light spectral band, helping to enhance the luminous efficiency and colour uniformity of the dual-layer remote phosphor package. The increase in (Ba,Sr)3BP3O12:Eu2+ however is not advantageous to the colour rendering index because of the lower red emission. The backscattered and back-reflected lights are degraded when the (Ba,Sr)3BP3O12:Eu2+ phosphor layer appears in the structure. The stable chromaticity and luminous flux at good values are observed when 10% weight percentage of (Ba,Sr)3BP3O12:Eu2+ is applied.

Applying the green Ca2Al3O6F:Eu2+ oxyfluoride phosphorus on white emitting diodes Van Liem Bui; Dieu An Nguyen Thi
Indonesian Journal of Electrical Engineering and Computer Science Vol 27, No 2: August 2022
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijeecs.v27.i2.pp754-759

Ca2Al3O6F:Eu2+, a new green-emitting and its photoluminescence (PL) characteristics for white-emitting diodes, have been analyzed and generated (w-LEDs). This phosphorus displays a strong absorption range between ultraviolet (UV) and blue region, along with a wide green emission range of 502 nm. The procedure for concentration suppression and Eu2+ luminous longevity has been investigated using Ca2Al3O6F:Eu2+ phosphors. Key characteristics for manufacturing w-LED lamps, such as photoluminesce based on temperature, microstructure, morphology, CIE value and quantum efficiency, were also investigated in Ca2Al3O6F:Eu2+. The findings show that Ca2Al3O6F:Eu2+, is a suitable option for almost UV-excited w-LEDs as a green component.

Synthesis and photoluminescence properties in white light-emitting diodes of oxynitride green phosphor Ba3Si6O12N2 Dieu An Nguyen Thi; Phan Xuan Le
Indonesian Journal of Electrical Engineering and Computer Science Vol 27, No 3: September 2022
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijeecs.v27.i3.pp1264-1269

Utilizing boron-coated Eu2O3, highly effective Ba3Si6O12N2 green-emitting phosphors were made using a gas reduction nitridation technique under flowing NH3 gas. We found that the synthesized phosphor is a pure phase of Ba3Si6O12N2 based on X-ray diffraction patterns. By modifying an alumina boat crystallized, the Ba3Si6O12N2 green-emitting phosphors from the result were considerably better and had higher emission intensity. Under stimulation at 405 nm, the radiation spectra revealed a typical wide green radiation band attributable to the 4f65d → 4f7 electronic transfer of Eu2+ ions. Generally, the green-emitting Ba3Si6O12N2 phosphors that were created by that method with boron-coated Eu2O3 is a potential phosphor-transformed diodes which emit white illumination white light emitting diodes(pc-WLEDs') element.

Higher chromatic rendition with Cr3+-doped yellow Y3Al5O12:Ce3+ for double-layer remote phosphor white-light-emitting diodes Dieu An Nguyen Thi; Phuc Dang Huu; Thuy Hang Nguyen Thi
International Journal of Electrical and Computer Engineering (IJECE) Vol 12, No 6: December 2022
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijece.v12i6.pp5872-5879

Remote phosphor designs of white-light-emitting diodes (WLEDs) have been recognized for their high thermal stability and excellent luminous efficiency but not for the chromatic rendering. The study presents an approach for the remote phosphor structure to overcome the low-color-rendering issue by enriching its red-light spectral intensity through co-doping Cr3+ and Ce3+ ions into the yellow Y3Al5O12 (YAG) phosphor compound. This ion co-doping process probably enhances emission spectra in the far-red range because of the energy transfer of the integrated ions: Ce3+ Cr3+. Additionally, the luminescence and color properties of the phosphor layer significantly depend on the doped concentration of the Cr3+ ion. Here, with 0.008% Cr3+ in the phosphor composite, either internal or external quantum performances of the dual-layer WLED light are enhanced, which achieved the number of 58.9% and 46.7%, respectively. The color rendering index (CRI) would also be higher if Cr3+ is added, about 77.9, compared to the CRI of 63.2 when using the original YAG:Ce3+ phosphor layer.

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