Wyniki wyszukiwania - BazTech

1

Comparison between SEPs of CaCO3 and TiO2 in phosphor layer for better color uniformity and stable luminous flux of WLEDs with 7,000 K

Le Phan Xuan, Trang Tran Thanh, Anh Nguyen Doan Quoc, Lee Hsiao-Yi, Tho Le Van

Materials Science Poland

|

2022

|

Vol. 40, No. 1

1--8

EN

CaCO3 and TiO2 are proposed in this study as particles for scattering enhancement (SEPs) of phosphor-converted white light-emitting diodes (pc-WLEDs). The use of these two SEPs for scattering improvement enables boosting of the color homogeneity of the WLED devices. Each SEP is mixed with YAG:Ce3+ and silicone composition to examine their optical influences and performances on the high-power WLED packages with 7,000 K color temperature (CT). Miescattering theory is applied to calculate and investigate the scattering elements - scattering coefficients, anisotropic scattering, the reduced scattering, and scattering amplitudes - at the wavelengths of 450 nm and 550 nm. The results exhibit that TiO2and CaCO3 considerably promote higher color uniformity and color-deviated reduction, respectively. The obtained results could be primarily attributed to the significant improvement in the scattering properties of the structure. Additionally, the effects of the presented scattering enhancement on luminous efficiency are displayed. The reduction in lumen output is observed to have a close connection with the concentration and particle size of TiO2and CaCO3, which means that control must be exercised over these factors when utilizing these SEPs for WLED fabrication.

2

Triple-layer remote phosphor structure: A potential packaging configuration to enhance both color quality and lumen efficiency of 6,000–8,500 K WLEDs

Le Phan Xuan, Ho Sang Dang, Anh Nguyen Doan Quoc, Lee Hsiao-Yi

Materials Science Poland

|

2021

|

Vol. 39, No. 4

458--466

EN

To achieve further enhancement in the lighting quality of white light-emitting diodes (WLEDs), this study proposed apackaging structure with three different phosphor layers, called triple-layer remote phosphor structure. This structure can provide an overall control over the light color distribution of WLEDs. The yellow-green-emitting CaAl2O4:Mn2+ phosphor andredemitting CaMoO4:Eu3+ phosphor are used along with the original yellow-emitting YAG:Ce3+phosphor to fabricate thetriple-layer structure. The concentration of yellow-emitting YAG:Ce3+phosphor is required to be decreased as the concentrations of other phosphors increase to keep the predetermined correlated color temperatures. The color rendering index (CRI) and the color quality scale (CQS) are measured to reach a thorough color quality assessment for WLEDs. The color management can be achieved by adjusting the concentration of red-emitting CaMoO4:Eu3+ phosphor to enhance the red emission. In addition, adjustment of the concentration of yellow-green-emitting CaAl2O4:Mn2+ phosphor can result in higher luminousefficiency owing to its control over the green light components. Higher CRI is observed when CaMoO4:Eu3+ concentration increases, while an increase in CaAl2O4:Mn2+ phosphor leads to much lower CRI. The CQS – on the other hand – is remarkably high when the CaMoO4:Eu3+ concentration range is about 10wt%–14wt%, regardless of the proportion of the CaAl2O4:Mn2+ phosphor. Furthermore, 40% enhancement in luminous efficiency is also achieved since light scattering is minimized by the boosted green-light emission spectra. Manufacturers can take these findings as reference to fabricate high-quality WLED lights that fulfill all their requirements.

3

The impacts of Ba2Li2Si2O7:Sn2+,Mn2+ and CaMgSi2O6:Eu2+,Mn2+ particles on the optical properties of remote phosphor LED

Chen Ming-Jui, Loan Nguyen Thi Phuong, Tho Le Van, Bui Thuc Minh, Le Phan Xuan, Anh Nguyen Doan Quoc, Liao Hsing-Yuan, Chang Jui-Chen, Lee Hsiao-Yi

Materials Science Poland

|

2020

|

Vol. 38, No. 1

197--205

EN

As implied in the title, the triple-layer remote phosphor (TRP), constructed with the yellow YAG:Ce3+ layer at the bottom, the red CaMgSi2O6:Eu2+,Mn2+ phosphor layer on the top, and the green Ba2Li2Si2O7:Sn2+,Mn2+ phosphor layer between these two layers, is suggested in this paper to improve the color and luminescence of white LEDs (WLEDs). In order to control the red light for the purpose of increasing the color rendering index (CRI), it is suggested that the red CaMgSi2O6:Eu2+,Mn2+ phosphor should be applied in the TRP structure. Simultaneously, the structure uses the green Ba2Li2Si2O7:Sn2+,Mn2+ phosphor layer to control the green light, which increases the luminous efficacy (LE) of WLEDs. In addition, when the concentration of these two phosphors increases, the yellow YAG: Ce3+ concentration must be reduced to keep the average correlated color temperatures (ACCTs) stable at 6000 K to 8500 K. Besides, appropriate adjusting of CRI, LE, and color quality scale (CQS) is also analyzed by modifying the concentration of the green phosphor and red phosphor. The results show that the CRI can get better values if CaMgSi2O6:Eu2+,Mn2+ concentration is higher. In contrast, the CRI decreases dramatically when the concentration of Ba2Li2Si2O7:Sn2+,Mn2+ increases. Meanwhile, CQS can be significantly increased in the range of 10 % to 14 % CaMgSi2O6:Eu2+,Mn2+, regardless of the concentration of Ba2Li2Si2O7:Sn2+,Mn2+. In particular, along with the improvement of CRI and CQS, LE can also be increased by more than 40 % by reducing the scattered light and adding the green light. Obtained results are a valuable reference for manufacturers for improving WLEDs color and luminescence quality to produce a broader range of WLEDs with better quality fulfilling social needs.