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All Journal International Journal of Electrical and Computer Engineering TELKOMNIKA (Telecommunication Computing Electronics and Control) Bulletin of Electrical Engineering and Informatics Indonesian Journal of Electrical Engineering and Computer Science
Dieu An Nguyen Thi
Industrial University of Ho Chi Minh City
Computer Science & IT Electrical & Electronics Engineering

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The improvement of the color rendering index using convex-dual-layer remote phosphor geometry with YOCl:Eu3+ Dieu An Nguyen Thi; Binh Le Nguyen Hoa
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 21, No 2: April 2023
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v21i2.24746

Abstract

White-light emitting diodes (WLEDs) are semiconductor light sources whose construction design is usually made up of a single pumping chip and a single light-conversion film of phosphor compound. The outstanding problem of this traditional setting is the inadequate chroma rendering index (CRI). Introducing a cluster of multiple blue chips with more than one phosphor layer is demonstrated to address that flaw of W-LEDs. This package is called the dual-film remote-phosphor multi-chip WLED. As a consequence, both the light brightness and the CRI are improved. However, for the maximum results, the test on the second layer of phosphor has been performed to continually alter the proportions and densities of phosphor within the silicone. The researchers employed a unique hue design to control the white-light light emitting diode (LED) module. When comparing the actual result to the simulated color coordinates under the hue standard of international commission on illumination (CIE) 1931, the highest difference is found to be around 0.0063 for correlated color temperatures (CCT) of 6600 K and 7700 K. Experiments indicate that the setting of multi-chip and dual-phosphorus is the optimal design for supporting CRI quality and luminous intensity.
CaO:Tb3+ green-emitting phosphor for white light-emitted diode-phosphor applications: the improvement of light output intensity Ha Thanh Tung; Dieu An Nguyen Thi
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 Ha Thanh Tung; Dieu An Nguyen Thi
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 Ha Thanh Tung; Dieu An Nguyen Thi
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.
The use of CaO:Eu3+ and Zn2SiO4:Mn2+ phosphors to increase the color quality and illumination intensity of WLEDs Ha Thanh Tung; Dieu An Nguyen Thi; Phan Xuan Le
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.v12i6.4754

Abstract

The lumen efficacy in remote phosphor structure displayed remarkable enhancements, which is notable for the development of white light-emitting diodes (WLEDs). Nevertheless, its quality of colour is deemed not as good as that of the conformal or in-cup phosphor structure. Therefore, the goal of this research is to achieve a better quality of colour and significant luminous flux value for remote phosphor configuration by using extra phosphor layers. In particular, the two-layer and three-layer structures with the implementation of green and red phosphors are proposed. Comparing these two structures can help pinpoint the best suited for the WLED production. The assessment of each structure’s effect on the WLEDs’ optical parameters was determined under various correlated temperatures of colour (5,600-8,500 K). The outcomes indicated that the three-layer structure enhanced the quality of colour with greater efficiency compared to the two-layer structure due to the increased color rendering index (CRI), color quality scale (CQS), and photoluminescence (PL), and reduced colour deviation. The scattering improvement of the three-layer structure is a key factor of these accomplishments, proven by the scattering theory of Mie. Therefore, the three-layer structure is potential for developing WLED production.
Utilizing SrSi2O2N2:Eu2+,Yb2+ phosphor to achieve high hue rendering index and high hue stability Ha Thanh Tung; Dieu An Nguyen Thi
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 Binh Le Nguyen Hoa Ha Thanh Tung Hoang Nam Nguyen Huu Phuc Dang Jan Nedoma Le Anh Vu My Hanh Nguyen Thi Nguyen Thi Phuong Thao Phan Xuan Le Phan Xuan Le Phuc Dang Huu Phung Ton That Thuy Hang Nguyen Thi Van Liem Bui