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All Journal TELKOMNIKA (Telecommunication Computing Electronics and Control) Bulletin of Electrical Engineering and Informatics Indonesian Journal of Electrical Engineering and Computer Science
Ha Thanh Tung
Vinh Long University of Technology Education
Computer Science & IT Electrical & Electronics Engineering

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Study of Ba2Li2Si2O7:Eu2+ phosphor for enhancing the luminous flux of white LEDs Ha Thanh Tung; Huu Phuc Dang
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 21, No 3: June 2023
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v21i3.24748

Abstract

The best spectrum characteristics and photometric productivities of white light emitting diode (WLED) device possessing light emitting diodes (LEDs) in red rather than phosphor pc/R-WLEDs with the hue fidelity index (Rf) > 97 for correlated color temperatures (CCTs) between 2700 K and 6500 K were attained using the illumination effectiveness (LE) model. We demonstrate four practical pc/R-WLEDs that have indices of Rf and LE of 96–97 and 120–124 lm/W, respectively, under CCT values measured at 2969 K, 4468 K, 5682 K, as well as 6558 K. These LED packages use blue and red LEDs, also phosphors in green as well as yellow, with respective wavelengths of 448 nm, 650 nm, 507 nm, and 586 nm. In the comparison between phosphor-transformed WLED devices (with phosphor conversion) and quantum-dot WLED devices (QD-WLEDs), pc/R-WLEDs make an outstanding performance in competitiveness for high hue generation, particularly under small CCT values, and could eventually replace current pc-WLEDs.
Using phosphor ZnB2O4:Mn2+ for enhancing the illuminating beam and hue standard in white light-emitting diodes Ha Thanh Tung; Huu Phuc Dang
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 21, No 3: June 2023
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v21i3.24749

Abstract

The enhancement in hue uniformity and luminous production of multiple-chip white LED lamps (MCW-LEDs) using dual-layer remote phosphor packaging designs are the emphases of this paper. We blended Mn2+ activated strontium–barium silicate (ZnB2O4:Mn2+) with the phosphor mixture and manage to record significant impacts of this new phosphor mixture on the LED lights’ lighting performance. There is evidence that the growing concentration of yellow-green-emitting ZnB2O4:Mn2+ phosphor encourages the enhancement of hue uniformity and illumination effectiveness in MCW-LEDs with mean correlated hue heats (CCTs) of roughly 8500 K, though the color quality scale is gradually deteriorating. It is possible to successfully achieve such amazing MCW-LED performance if we choose the right concentration and size of ZnB2O4:Mn2+.
The better distant phosphor configurations for enhancing WLED color intensity: YVO4:Eu3+ and YF3:Mn2+ Ha Thanh Tung; Huu Phuc Dang
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.v21i2.24747

Abstract

The distant phosphor configuration produces more illuminating beams than the two settings containing conformal or in-cup phosphor. When this configuration is used, though, it is difficult to manage the color standard of light-emitting diodes (LEDs). As a result, in past few years, numerous studies have focused on controlling the color standard of distant phosphor configurations. Until present, two distant phosphor configurations of single- and triple-film phosphor configurations, have been used to improve color standards. This research will investigate the ideal configuration among these configurations in terms of color rendering index (CRI), color quality scale (CQS), lumen output (LO), as well as color homogeneity for multi-chip white LEDs (WLEDs). WLEDs, operating at five different temperatures of color between 5600 K and 8500 K, are used to perform the studies. The results reveal that the three-sheet phosphor setting would be more desirable, with greater CRI, CQS, and lumen efficiency (LE) indexes. Furthermore, when using a triple-layer phosphor arrangement, color variation is reduced, resulting in a rise in color consistency. This conclusion is possibly verified by using Mie theory to analyze scattering properties in distant phosphor setup, making the study findings legitimate and important data to produce more advanced WLEDs.
Impact of CuS counter electrode calcination temperature on quantum dot sensitized solar cell performance Le Thi Ngoc Tu; Ha Thanh Tung
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 21, No 5: October 2023
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v21i5.25118

Abstract

In place of the commercial Pt electrode used in quantum sensitized solar cells, the low-cost CuS cathode is created using electrophoresis. High resolution scanning electron microscopy and X-ray diffraction were used to analyze the structure and morphology of structural cubic samples with diameters ranging from 40 nm to 200 nm. The conversion efficiency of solar cells is significantly impacted by the calcination temperatures of cathodes at 100 °C, 120 °C, 150 °C, and 180 °C under vacuum. The fluorine doped tin oxide (FTO)/CuS cathode electrode reached a maximum efficiency of 3.89% when it was calcined at 120 °C. Compared to other temperature combinations, CuS nanoparticles crystallize at 120 °C, which lowers resistance while increasing electron lifetime. In place of the commercial Pt electrode used in quantum sensitized solar cells, the low-cost CuS cathode is created using electrophoresis. High resolution scanning electron microscopy and X-ray diffraction were used to analyze the structure and morphology of structural cubic samples with diameters ranging from 40 nm to 200 nm. The conversion efficiency of solar cells is significantly impacted by the calcination temperatures of cathodes at 100 °C, 120 °C, 150 °C, and 180 °C under vacuum. The fluorine doped tin oxide (FTO)/CuS cathode electrode reached a maximum efficiency of 3.89% when it was calcined at 120 °C. Compared to other temperature combinations, CuS nanoparticles crystallize at 120 °C, which lowers resistance while increasing electron lifetime.
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.
The effects of Ca14Mg2(SiO4)8:Eu2+ phosphor on white light emission quality of LED-phosphor packages Ha Thanh Tung; Dieu An Nguyen Thi; Nguyen Doan Quoc Anh
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.v12i6.4792

Abstract

Ca14Mg2(SiO4)8: Eu2+ (CMS:Eu2+) green phosphor is used for creating the white-light emitting diode (W-LED) packages with conversion phosphor materials. The phosphor shows the broadband green emission that peaks at 505 nm in the blue wavelength. The phosphor introduces the improvement in the blue and green emission spectra, which helps to heighten the luminous flux. Moreover, that the concentration of CMS:Eu2+ increases, the scattering events are enhanced to benefits the color blending for lower color variations or better color uniformity. The color renditions reduce with the rising green-phosphor concentration. The green-light amount becomes surplus and redundant for balancing color elements of white light emission. Thus, it should adjust and keep the concentration of CMS:Eu2+ in the range of ~2–8 wt%, to get the average number of color rendering index (CRI) (73–75), and color quality scale (CQS) (60–64). The CMS: Eu2+, hence, is suitable for white light realization, and the W-LED aiming at high-luminescence white light emission with improved color uniformity, and average rendering performances.
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 Dieu An Nguyen Thi Dieu An Nguyen Thi Hoang Thinh Nhan Huu Phuc Dang Huu Phuc Dang Huynh Thanh Thien Le Thi Ngoc Tu My Hanh Nguyen Thi Nguyen Doan Quoc Anh Nguyen Le Thai Phan Xuan Le Phung Ton That