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Effects of titanium dioxide quantum dots on the color deviation and luminous flux of white light-emitting diodes Thanh Binh Ly; Phung Ton That; Phan Xuan Le
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.pp611-617

The application of quantum dots has been considered as a promising approach to the advancement of phosphor-converted light-emitting diodes (pc-LEDs) since they perform an excellent extinction coefficient. Yet, it is challenging to manage their influences on the optical properties of LEDs due to their different nanometers in size. Hence, the object of this research is to analyze the influences of quantum dot (QDs) to figure out the solution to control the enhancement of LED lighting performances. Particularly, the study worked on investigating the scattering and absorption features of titanium dioxide (TiO2) QDs. It demonstrated that the radiant efficiency and luminous stability of the TiO2 QDs-converted LEDs (QC-LEDs) was inferior due to the strong light absorption and reabsorption occurring inside the LED packages. Additionally, it also presented low uniformity of color distribution because the scattering ability of QDs is weak. Therefore, reducing the concentration of QDs when adding to the LED structure seems to be possible to enhance the luminous output of QC-LEDs. We propose 0.05% wt. TiO2 for white LED to reduce the illumination losing caused by re-absorbent and total internal backscattering, resulting in approximate 31% lumen improvement and high color rendering index (CRI) measured at about 85, at a high color temperature of 7500 K.

The application YAG:Ce3+@SiO2 phosphor for improving color deviation of phosphor-converted light-emitting diode Thanh Binh Ly; Phan Xuan Le
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.pp618-625

The yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce3+), which sees its most popular use in white light-emitting diode (wLEDs), possess an optical spectrum that lacks the red element. The following article will propose a fresh solution for this problem, which involves adjusting the properties of Ce3+ spectrum by using exterior dye particles of ATTO-Rho101, possessing dramatic, wide absorption within the zone of green-yellow spectrum of Ce3+ emission and significant release of the red element. The globular YAG:Ce3+, which is micrometer and nanometer in size with significant dispersion (micro/nano-YAG:Ce3+) was created by employing an altered solvothermal technique. The YAG:Ce3+ produced by said technique, along with the heated micro-YAG:Ce3+ and commercial phosphors, were exteriorly covered with SiO2 and immersed in dye at the same time. Effective radiant transmission/reabsorption from Ce3+ within the YAG’s internal bowel to the dye particles of the exterior hull of SiO2, regardless of the phosphors’ size, was displayed in the YAG: Ce3+@SiO2+ dye powder amassed over the stimulation of the light of blue, which boosted the red element of it. The fluorescent microscope was considered an effective device intended for detecting the reabsorption event in grinded substances.

Investigation of MAl2−xSixO4−xNx:Eu2+ phosphor for improving luminescence properties of white LEDs Thanh Binh Ly; Phan Xuan Le
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.pp626-631

We implement a solid-state reaction technique to make MAl2−xSixO4−xNx (M = Ca, Sr, Ba) as well as its variant doped with Eu at 1300 – 1400°C in a nitrogen hydrogen environment. Then, we measure the solubility of (SiN)+ in MAl2O4. By replacing (AlO)+ with (SiN)+, whose solubility is dependent on M cations, nitrogen may be integrated into MAl2O4. (SiN)+ has poor solubility in CaAl2O4 (x ≈ 0.025) and SrAl2O4 lattices (x ≈ 0.045) but a considerable integrated quantity of (SiN)+ against BaAl2O4 (x ≈ 0.6). Because of the low solubility of (SiN)+, incorporation of (SiN)+ barely affects the luminescence characteristics of MAl2O4 when doped with Eu2+ (M = Ca, Sr), resulting in discharges in green as well as blue at nearly constant wavelengths measured at 440 as well as 515 nm, respectively. With certain concentrations of (SiN)+ as well as Eu2+, Eu2+-doped BaAl2−xSixO4−xNx emits one wide green discharge line under a maximum within the region 500 – 526 nm. Furthermore, once we add nitrogen, both the excitation as well as discharge lines for Eu2+ exhibit one substantial redshift. BaAl2−xSixO4−xNx: Eu2+ is a compelling transmuting phosphor that can be utilized for WLED devices because of its efficient stimulation in the range of 390–440 nm radiation.

TiO2 nanoparticles impacts over color deviation in white light-emitting diodes Thanh Binh Ly; Nguyen Doan Quoc Anh; 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.pp1304-1310

The effects of injecting TiO2nanoparticles with phosphorus silicone packing on white color light-emitting diodes (WLEDs) are examined. In WLED packages, the proposed approach may increase luminance emission by 2.7%, while the coordinated color temperature will increase by 39%. At the same time, the required phosphorus quantity will be lowered by 5% along with the joint temperature of 6.5°C. The modifications, which boost illuminating performance and also reduce temperature aggregation, are because of the packing material's increased illuminating dispersion efficiency or even refracting indices, along with lower illuminating reduction, for which colour fusing inside the parcels is responsible. Consequently, the results suggest improved-WLED lighting system performance makes the products more appropriate in solid-state lighting.

Improving optical properties of white light-emitting diodes using triple-layer remote structure Thanh Binh Ly; 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.pp1242-1250

Inrecent efforts to improve the performance ofwhite light-emitting diode (WLEDs), researchers have focused on angular color uniformity (ACU), an effective index for evaluating the light quality of WLEDs. Inthis article, we also aim for the WLED development by applying three phosphor layers in the remote phosphor structure. The dual-layer phosphor (DLP) remote structure is also included in the research for comparison with the triple-layer phosphor (TLP) in terms of their impacts on the lighting quality of WLEDs. To ensure the diversity and applicability in different scenarios, performancesof multi-layer phosphor structures in WLED devices with average correlatedcolor temperatures (ACCTs) from 5600 K to 8500K are measured. The experimental results have proved that both TLP and DLP structures are suitable to enhance WLEDs’ performance as each structure excels at specific qualities. In particular, at all ACCTs, the DLP structure is getting better in improvingthe color rendering index (CRI), while the TLP is more advantageous to color quality scale (CQS) and light output. The TLP also presents a lower color deviation than the DLP does, which leads to a better color uniformity in WLEDs at all ACCTs.

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