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All Journal International Journal of Electrical and Computer Engineering Bulletin of Electrical Engineering and Informatics
Nguyen Thi, Dieu An
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Computer Science & IT Electrical & Electronics Engineering

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Application of green-emitting ZnS:Eu2+ for boosting the spectrum of white light-emitting diode packages Nguyen Thi, Dieu An; Dang Huu, Phuc
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

Abstract

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.
CaO:Tb3+ green-emitting phosphor for white light-emitted diode-phosphor applications: the improvement of light output intensity Tung, Ha Thanh; Nguyen Thi, Dieu An
Bulletin of Electrical Engineering and Informatics Vol 13, No 1: February 2024
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/eei.v13i1.4753

Abstract

The use of CaO:Tb3+ with light green emission on for improvement of both luminescent output and chromatic fidelity of the white light emitted from a light-emitting diode (LED). The CaO:Tb3+ is combined with the yellow-emitting phosphor of YAG:Ce3+ to provide sufficient colored spectral proportion for the white light generation, enhancing the color performance. The phosphor combination is utilized for the three most applied LED structures: conformal, in-cup, and remote phosphor structures. The changes in optical properties of these three LEDs are monitored with adjustments in the proportion of CaO:Tb3+. The higher proportion of the green phosphor results in higher scattering efficiency in all structures, offering better color coordination and stronger luminous flux. The color quality scale is somehow reduced when CaO:Tb3+ concentration is more than a certain level. Therefore, depending on the phosphor configuration of the white light-emitting diode (WLED), the concentration of CaO:Tb3+ should be modified to achieve a good color rendition with improved color consistency and luminous properties.
White light-emitting diode daubed via CaSc2O4:Ho3+/Yb3+ nanocrystal sheets enclosed using SiO2 Tung, Ha Thanh; Nguyen Thi, Dieu An
Bulletin of Electrical Engineering and Informatics Vol 13, No 1: February 2024
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/eei.v13i1.4971

Abstract

Our investigation assesses the downshifting (DS), periodicity up-transmutation as well as internal light consistency from phosphor samples of CaSc2O4 incorporated with Ho3+/Yb3+ along with up-conversion from CaY2O4 incorporated with Ho3+/Yb3+. These samples are created via precursor antecedent compound technique. The generation for the crystalline samples having orthorhombic stage is validated by the X-ray powder diffraction. The dispersal reflectance spectra exhibit several lines within the zones of ultraviolet–visible–near infrared (UV-vis-NIR), resulting from the ions of Ho3+ as well as Yb3+. The optical band gap (Eg) results reach 5.69 and 5.58 eV, corresponding to CaSc2O4:Ho3+/Yb3+ and CaY2O4:Ho3+/Yb3+. The CaSc2O4:Ho3+/Yb3+ samples exhibit potent downshifting discharge in green hue when excited under 454 nm. CaSc2O4:Ho3+/Yb3+, as well as CaY2O4:Ho3+/Yb3+, exhibit potent discharges in green hue as well as near-infrared up-transmutation discharges in faint blue and red hues when excited under 980 nm. The spectrum hue clarity -Sgr – for CaSc2O4:Ho3+(1%)/Yb3+(5%) reaches 0.78. The disparity in pumping force yields internal light consistency for said sample with the green discharge, being nonexistent in the CaY2O4:Ho3+(1%)/Yb3+(5%) sample. As such, CaSc2O4:Ho3+/Yb3+ may prove useful when applied to up-transmutation apparatuses.
Thermal consequences of sintering the borosilicate matrix blue-green color release properties Tung, Ha Thanh; Nguyen Thi, Dieu An
Bulletin of Electrical Engineering and Informatics Vol 12, No 6: December 2023
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/eei.v12i6.4723

Abstract

Color transformation glass ceramics were produced of borosilicate matrix co-doped (SrBaSm)Si2O2N2:(Eu3+Ce3+) blue–green (B-G) (abbreviated as (SBS)SON:(EuCe) B-G) phosphors using a two-step co-sintering technique. The shift in illumination characteristics and drift of chromaticity coordinates (CIE) of (SBS)SON:(EuCe) (B-G) phosphors and hue transformation glass ceramics were investigated over a 600–800 ºC sintering thermal range. With rising sintering heat, the illuminated strength and inner quantum yield (QY) of (abbreviated as B-G) phosphors and glass ceramics reduced. Once the sintering heat was raised above 750 ºC, the phosphors and hue transformation glass ceramics showed nearly no high point among their luminescence photoluminescence (PL) and photoluminescence excitation (PLE) bands of color. B-G phosphors have low heating steadiness at more elevated temperatures, according to the findings. The glass matrix destructed the phosphors lattice layout and the Ce3+ in the phosphors was oxidized to Ce4+, resulting in a reduction in the luminous characteristics of the color transformation glass ceramics.
Utilizing SrSi2O2N2:Eu2+,Yb2+ phosphor to achieve high hue rendering index and high hue stability Tung, Ha Thanh; Nguyen Thi, Dieu An
Bulletin of Electrical Engineering and Informatics Vol 13, No 1: February 2024
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/eei.v13i1.4724

Abstract

For white-light emitting diode (WLED) applications, a green-to-orange emission nitridosilicate-based phosphor is created. The observed wide-band radiation in the green-orange range is caused by Eu2+ and Yb2+ at the trap point of a doubly doped SrSi2O2N2:Eu2+,Yb2+ (SSON:Eu,Yb) nitridosilicate phosphor. The green-color radiation’s decay duration was measured to validate the energy transfer among activator ions. The co-doping various ratios’ influence of activator ions on luminescence features was investigated. The resulting phosphor’s radiation is a function of the activator ion concentrations and raising the Yb2+ concentration causes red-color radiation to dominate the green radiation. To generate white illumination, the resulting phosphor was coupled with an InGaN blue-LED chip having a pumping wavelength of 450 nm. Two stages were taken to achieve hue balance management. Initially, the green to orange proportion was tuned by varying the Eu2+ and Yb2+ ions’ concentrations. At the second stage, the Commission Internationale de L’Eclairage, International Commission on Illumination (CIE) coordinates were changed from [0.2805; 0.2014] to [0.4071; 03789] by raising the amount of phosphor powder used. White illumination produced under optimal conditions has a hue rendering indicator of 89. The designed single-stage dual-hue-releasing nitridosilicate phosphor and blue-LED chip displayed remarkable hue steadiness over a wideband of forward-bias currents (100 to 500 mA at 3 V).
Co-Authors Dang Huu, Phuc Tung, Ha Thanh