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Journal : TELKOMNIKA (Telecommunication Computing Electronics and Control)

The application of Ca5B2SiO10:Eu3+ and YAl3B4O12:Ce3+,Mn2+ in dual-layer remote phosphor to enhance lumen output and color quality of WLEDs Phan Xuan Le; Le Hung Tien
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 19, No 5: October 2021
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v19i5.15024

Abstract

This study proposes a dual-layer remote phosphor structure, comprised of a green or a red phosphor layer and a yellow YAG:Ce3+ phosphor layer, to enhance color rendering index (CRI) and color quality scale (CQS) of white light-emitting diodes (WLEDs). The phosphors used in this study are green phosphor YAl3B4O12:Ce3+,Mn2+ and red phosphor Ca5B2SiO10:Eu3+. Besides, the applied WLED structure has the color temperature of 8500 K. The study demonstrates the idea of placing a green phosphor YAl3B4O12:Ce3+,Mn2+ or a red Ca5B2SiO10:Eu3+ phosphor layer on the yellow phosphor YAG:Ce3+ one. After that, the suitable concentration of Ca5B2SiO10:Eu3+ resulting in the highest color quality is determined. The obtained results showed that Ca5B2SiO10:Eu3+ is advantageous to CRI and CQS. Particularly, the values of CRI and CQS increased following the growth of Ca5B2SiO10:Eu3+ concentration, due to the rise in red light components inside WLED’s packages. Meanwhile, the luminous flux is benefited by the added green YAl3B4O12:Ce3+,Mn2+ phosphor. However, there are decreases in lumen output and color quality when the concentrations of Ca5B2SiO10:Eu3+ and YAl3B4O12:Ce3+,Mn2+ rise over the corresponding levels. This result is proved via using Mie-scattering theory and Lambert-Beer's law. In short, the findings of the research paper are valuable references for high-light-quality WLEDs fabrication.
Benefits of using TiO2 quantum dots in producing low-cost and high-quality white light-emitting diodes Phuc Dang Huu; Phung Ton That; Tran Thanh Trang; Phan Xuan Le; Nguyen Doan Quoc Anh
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 20, No 3: June 2022
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v20i3.15347

Abstract

Quantum dots (QDs) is considered as a potential material for the improvement of light-emitting diodes (LEDs). However, different from the traditional phosphor materials, they have unique scattering and absorption properties affected by their several nanometers sizes, which makes their application in the production of LED confront more challenges. In addition to this, their influences on QDs-converted LEDs (QCLEDs) are rarely investigated. So as to propose solutions for those problems, in this article, we experimentally and theoretically investigated the impacts of titanium dioxide (TiO2)QDs’ scattering and absorption on the light quality of QCLEDs by drawing a thorough comparison between their properties and the traditional yttrium aluminum garnet phosphors characteristics. The outcomes showed that QCLEDs have poor radiant efficacy and stability due to QDs’ strong characteristic of absorption (reabsorption) while their weak scattering property causes a low uniformity in correlated color temperature (CCT). For achieving high efficiency and stability white LEDs, we highly suggest using QDs with a low concentration to get reductions in the reabsorption and total internal reflection losses. With 0.05 concentration of TiO2 nanoparticles (TiO2 NPs), the white LEDs can simultaneously achieve a high CCT (approximately 7500 K) and a high color rendering index (around 85).
Integrating SiO2 nanoparticles to achieve color uniformity and luminous efficiency enhancement for white light emitting diodes Phan Xuan Le; Phung Ton That
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 19, No 5: October 2021
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v19i5.20484

Abstract

A phosphor structure with SiO2 nanoparticles is proposed to achieve the enhancement in the correlated color temperature (CCT) homogeneity and the luminescence performance for white light-emitting diodes (WLEDs). As SiO2 is integrated into the phosphorus compound, the scattering effect of this material contributes to better blue-light utilization. Thus, this innovative packaging design results in a significant increased lumen efficiency, more than 12%, in comparison with that of conventional dispensing ones. Meanwhile, the angular CCT deviation also decreases considerably, from 522 K to 7 K, between the angles of -70 and 700. Moreover, this reduction leads to the diminishment of yellow ring phenomenon effect. In addition, the measurement of haze demonstrates that there is a strong scattering in the visible spectrum when SiO2 is added into the silicone film. Besides that, when increasing the driving current, SiO2 stabilizes the chromaticity coordinate shift, which is a vital requirement for indoor lighting applications. Furthermore, SiO2 nanoparticles own excellent optical features, cost efficiency, and simple production will probably turn this material into a potential material in advancing the optical performance of WLEDs.