scholarly journals Research on adjustable correlated color temperature COB-LED light source based on flip chips and screen printing technology

2021 ◽  
Author(s):  
Rongrong Zhang ◽  
Zuojie Wen ◽  
Bingqian Li ◽  
Shenghua Liang ◽  
Mingde Yang ◽  
...  
Keyword(s):  
Light Source ◽  
White Light ◽  
Screen Printing ◽  
Light Emitting Diode ◽  
Luminous Flux ◽  
Color Temperature ◽  
Current Ratio ◽  
Led Light ◽  
Driving Current ◽  
Screen Printing Technology

Abstract Using the characteristic of flip light emitting diode (LED) chips without front-side welding wires, before applying fluorescent glue throughout the luminous surface, a part of the chips are directionally and quantitatively coated fluorescent glue by screen printing process, a chip on board (COB) white LED light source is developed with adjustable correlated color temperature (CCT). A part of the blue LED chips in the light source excites the fluorescent glue to produce a warm white light (CCT = 2631K), and the other part produces cool white light (CCT = 6181K). When changing the driving current ratio of the two parts of the chips, the CCT of COB LED light source can be continuously adjusted between warm and cool white light. According to the measured data, the relationship between the CCT and the driving current ratio of the two parts is obtained by fitting. Within the adjustable range of the CCT (2631 K to 6181 K), the color rendering index (CRI) is about 90. The minimum is 89.3 and the maximum is 93.1. While achieving adjustable CCT and high CRI, the LED light source has a luminous flux of 1938.76 lm on a circular surface with a diameter of 11 mm. The overall luminous efficiency is close to 100 lm/W.

scholarly journals Using CaCO3-doped package to improve correlated color temperature uniformity of white light-emitting diodes

2021 ◽  
Vol 11 (6) ◽  
pp. 4817
Author(s):  
My Hanh Nguyen Thi ◽  
Nguyen Thi Phuong Loan ◽  
Thuc Minh Bui ◽  
Hoang Van Ngoc
Keyword(s):  
White Light ◽  
Light Emitting Diode ◽  
Luminous Flux ◽  
Color Temperature ◽  
Resin Matrix ◽  
Light Emitting ◽  
Color Quality ◽  
Color Uniformity ◽  
Stability Enhancement ◽  
White Light Emitting Diodes

<span>The white light-emitting diode (WLED) has been the most advance lighting method currently, however, the fabrication process of this configuration still has drawbacks which negatively affect its color quality. This research was conducted to provide a method for WLED’s lighting output enhancement. Since CaCO<sub>3</sub> particles are excellent for thermal stability enhancement, especially when being combined with an adhesive substance, we decided to integrate CO<sub>3</sub> particles into resin matrix such as melamine formaldehyde (MF) and investigate their influences on the optical properties, including color uniformity and lumen output, of the WLED. The results showed that CaCO3 and MF resin are beneficial to the light scattering efficiency, which results in higher luminous flux and chromatic quality for WLED packages. In addition to that, the appropriate amounts of MF resin and CaCO<sub>3</sub> for reaching the best lumen efficiency and color quality are figured out at 1% and 10%, respectively. Moreover, another advantage of using MF resin and CaCO<sub>3</sub> for fabricating WLEDs is cost effectiveness. Hence, it has turned out that CaCO<sub>3</sub> and MF resins can be potential materials for next high-quality WLED generations.</span>

scholarly journals Analysis on High-Power Seaport LED Luminaire with Uniform Light Distribution Based on Optimized Lens and Heatsink

2021 ◽  
Vol 11 (9) ◽  
pp. 4035
Author(s):  
Jinsheon Kim ◽  
Jeungmo Kang ◽  
Woojin Jang
Keyword(s):  
Light Source ◽  
High Power ◽  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Light Distribution ◽  
Light Sources ◽  
Led Light ◽  
High Power Led ◽  
Distribution Requirement ◽  
Lighting Application

In the case of light-emitting diode (LED) seaport luminaires, they should be designed in consideration of glare, average illuminance, and overall uniformity. Although it is possible to implement light distribution through auxiliary devices such as reflectors, it means increasing the weight and size of the luminaire, which reduces the feasibility. Considering the special environment of seaport luminaires, which are installed at a height of 30 m or more, it is necessary to reduce the weight of the device, facilitate replacement, and secure a light source with a long life. In this paper, an optimized lens design was investigated to provide uniform light distribution to meet the requirement in the seaport lighting application. Four types of lens were designed and fabricated to verify the uniform light distribution requirement for the seaport lighting application. Using numerical analysis, we optimized the lens that provides the required minimum overall uniformity for the seaport lighting application. A theoretical analysis for the heatsink structure and shape were conducted to reduce the heat from the high-power LED light sources up to 250 W. As a result of these analyses on the heat dissipation characteristics of the high-power LED light source used in the LED seaport luminaire, the heatsink with hexagonal-shape fins shows the best heat dissipation effect. Finally, a prototype LED seaport luminaire with an optimized lens and heat sink was fabricated and tested in a real seaport environment. The light distribution characteristics of this prototype LED seaport luminaire were compared with a commercial high-pressure sodium luminaire and metal halide luminaire.

scholarly journals Near Unity PLQY and High Stability of Barium Thiocyanate Based All-Inorganic Perovskites and Their Applications in White Light-Emitting Diodes

Photonics ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 209
Author(s):  
Gopi Chandra Adhikari ◽  
Saroj Thapa ◽  
Yang Yue ◽  
Hongyang Zhu ◽  
Peifen Zhu
Keyword(s):  
White Light ◽  
Large Scale ◽  
Light Emitting Diode ◽  
Photophysical Properties ◽  
Environmental Stability ◽  
Color Temperature ◽  
Ambient Atmosphere ◽  
Light Emitting ◽  
Halide Perovskite ◽  
Lead Halide

All-inorganic lead halide perovskite (CsPbX3) nanocrystals (NCs) have emerged as a highly promising new generation of light emitters due to their extraordinary photophysical properties. However, the performance of these semiconducting NCs is undermined due to the inherent toxicity of lead and long-term environmental stability. Here, we report the addition of B-site cation and X-site anion (pseudo-halide) concurrently using Ba(SCN)2 (≤50%) in CsPbX3 NCs to reduce the lead and improve the photophysical properties and stability. The as-grown particles demonstrated an analogous structure with an almost identical lattice constant and a fluctuation of particle size without altering the morphology of particles. Photoluminescence quantum yield is enhanced up to near unity (~98%) by taking advantage of concomitant doping at the B- and X-site of the structure. Benefitted from the defect reductions and stronger bonding interaction between Pb2+ and SCN− ions, Ba(SCN)2-based NCs exhibit improved stability towards air and moisture compared to the host NCs. The doped NCs retain higher PLQY (as high as seven times) compared to the host NCs) when stored in an ambient atmosphere for more than 176 days. A novel 3D-printed multiplex color conversion layer was used to fabricate a white light-emitting diode (LED). The obtained white light shows a correlated color temperature of 6764 K, a color rendering index of 87, and luminous efficacy of radiation of 333 lm/W. In summary, this work proposes a facile route to treat sensitive lead halide perovskite NCs and to fabricate LEDs by using a low-cost large-scale 3-D printing method, which would serve as a foundation for fabricating high-quality optoelectronic devices for near future lighting technologies.

Research on COB-LED light source with tunable CCT based on screen printing and flip chip technology

2022 ◽  
Vol 54 (2) ◽  
Author(s):  
Rongrong Zhang ◽  
Zuojie Wen ◽  
Bingqian Li ◽  
Shenghua Liang ◽  
Mingde Yang ◽  
...  
Keyword(s):  
Light Source ◽  
Screen Printing ◽  
Flip Chip ◽  
Led Light ◽  
Chip Technology

Optical and structural properties of curcuminoids extracted from Curcuma longa L. for hybrid white light diode

2018 ◽  
Vol 84 (1) ◽  
pp. 10501 ◽  
Author(s):  
M. Al Shafouri ◽  
Naser M. Ahmed ◽  
Z. Hassan ◽  
Munirah Abdullah Almessiere ◽  
Maadh Jumaah
Keyword(s):  
White Light ◽  
Dye Degradation ◽  
Uv Light ◽  
Light Emitting Diode ◽  
Curcuma Longa ◽  
Stress Test ◽  
Air Gap ◽  
Color Temperature ◽  
Soxhlet Apparatus ◽  
Normal Method

In this study, curcuminoids were extracted from turmeric (Curcuma longa L.) by means of three methods, comprising the normal method, use of Soxhlet apparatus and by combining the normal method with the Soxhlet extraction approach. The limitation of stickiness in the use of curcuminoids was resolved by mixing it with silica gel. The curcuminoids used light down-conversion of UV light (390 nm) for the white light-emitting diode (WLED). The characteristics of the white light chromaticity were controlled by changing the current and concentration of the curcuminoids. The chromaticity coordinates (CIE) and correlated color temperature (CCT) were measured for different applied currents (20, 60 and 100 mA) and weights (25, 35 and 50 mg) of curcuminoids. It was observed from the concentration of phosphor that the combination of the normal and Soxhlet apparatus methods is most effective extraction approach. The results showed that increasing the concentration of phosphor significantly and remarkably increased the value of CCT when different values of current were applied. The stress test showed that the prolongation of dye degradation can be improved using air gap and glass slid, with air gap being more effective. An optimum color rendering index (CRI) value of 61.2 is obtained. The white phosphor exhibited CIE values of 0.333, 0.3151 and color temperature (CCT) of 5405 K.

scholarly journals Chromaticity Study of Curcumin Dye Extracted from Curcuma longa L. Using for UV Light down Conversion for White Light Emitting Diode

2019 ◽  
Vol 290 ◽  
pp. 183-189
Author(s):  
Mahmood Al Shafouri ◽  
Naser Mahmoud Ahmed ◽  
Zainuriah Hassan ◽  
Munirah Abdullah Almessiere
Keyword(s):  
White Light ◽  
Uv Light ◽  
Light Emitting Diode ◽  
Curcuma Longa ◽  
Color Temperature ◽  
Light Emitting ◽  
Chromaticity Coordinates ◽  
Major Factors ◽  
Color Rendering ◽  
Down Conversion

In thus study, Turmeric phosphor dye was extracted from Curcuma Longa L. via a simple technique using silica gel. The phosphor was used for light down-conversion of UV light for the manufacture white light emitting diode (WLED). The UV-LED was analyzed over 395nm wavelengths. The characteristics of the white light chromaticity were controlled by tuning the current and phosphor concentration. An optimum color rendering index (CRI) value of 63.4 was obtained. The chromaticity coordinates (CIE) and correlated color temperature (CCT) were measured for various currents and phosphor concentrations. The white phosphor exhibited CIE value of 0.355,0.338 and CCT of 4567 K. The concentration of phosphor and amount of applied current were confirmed to be major factors that control the intensity of white light emitted from the sample, where CIE and CRI of the emitted light steadily increased with the concentration of phosphor and current. Thus, phosphor concentration has a critical effect on conversion efficiency. Key words: Turmeric, phosphor, WLED, curcumin

1.331μm Narrow-Bandwidth Light Source Based on Polymer Micro-Blazed Grating

2008 ◽  
Author(s):  
Hairong Wang ◽  
Xianni Gao ◽  
Guoliang Sun ◽  
Yulong Zhao ◽  
Zhuangde Jiang
Keyword(s):  
Light Source ◽  
Light Emitting Diode ◽  
Low Cost ◽  
Diffraction Order ◽  
Blazed Grating ◽  
Light Emitting ◽  
Led Light ◽  
Narrow Bandwidth ◽  
Narrow Width ◽  
The Cost

In order to detect methane (CH4) accurately and reliably, this paper presents a sensor which consists of infrared diode, fixtures, blazed grating, to realize the extremely narrow-bandwidth light at wavelength of 1.331μm. Based on factors such as compatibility with the transmission characteristics of silica fiber and the cost, a LED (light-emitting diode) with center wavelength of 1.3μm is selected. The LED light is modulated as the parallel light beam. As the light is incident in a micro-blazed grating with certain angle, by diffraction and interference, the light will output the maximum light intensity of its diffraction order at 1.331 μm, which just is an absorption peak of CH4. Micro-blazed grating applied here is low cost and easy replication by various ways, which makes extreme narrow width wavelength possible. Simulation and analysis indicate the designed prototype can output 1.331μm with bandwidth from 1.32907μm to 1.332495μm. With the light source basing on light dividing system, more reliable and higher sensitive measurement of the dangerous gases such as methane and carbon monoxide (CO) can be realized.

Screen-Printing of Yellow Phosphor Powder on Blue Light Emitting Diode (LED) Arrays for White Light Illumination

2007 ◽  
Author(s):  
K. H. Lee ◽  
S. W. Ricky Lee
Keyword(s):  
White Light ◽  
Screen Printing ◽  
Light Emitting Diode ◽  
Light Illumination ◽  
Light Emitting ◽  
Yellow Phosphor ◽  
Coating Methods ◽  
Phosphor Coating ◽  
White Light Illumination ◽  
Led Arrays

In current technology, white light generation from a light emitting diode (LED) can be achieved by combining the lights from three fundamental colors, namely, red, green and blue (RGB), of LEDs or by coating a phosphor layer onto the surface of a LED chip. The first method involving the RGB color mixing technique requires a complicated electrical circuit design for the control of light intensity and uniformity on the three different colors of LEDs and hence increases the costs of manufacturing. The second method is implemented by coating a layer of yellow phosphor on a blue LED chip for white light illumination. The quality of generated white light heavily depends on the packing density, the thickness and the uniformity of the phosphor coating. There have been some coating methods available in the industry. Each one of them has its own pros-n-cons. In the present study, a new yellow phosphor coating method by screen-printing on blue LED arrays is developed. Compared with conventional coating methods, this screen-printing method is considered relatively simple and rather effective. The newly developed method and the results of prototyping are introduced in this paper in detail.

scholarly journals High Efficiency and Color Rendering Quantum Dots White Light Emitting Diodes Optimized by Luminescent Microspheres Incorporating

Nanophotonics ◽  
2016 ◽  
Vol 5 (4) ◽  
pp. 565-572 ◽  
Author(s):  
Wei Chen ◽  
Kai Wang ◽  
Junjie Hao ◽  
Dan Wu ◽  
Jing Qin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
White Light ◽  
High Efficiency ◽  
Lattice Structure ◽  
Light Emitting Diode ◽  
Luminescent Properties ◽  
Color Temperature ◽  
High Quantum Efficiency ◽  
Light Emitting ◽  
Color Rendering

AbstractIn this research, we have developed an approach by incorporating quantum dots (QDs) with red emission into mesoporous silica microspheres through a non-chemical process and obtained luminescent microspheres (LMS). Owing to the lattice structure of LMS, QDs were effectively protected from intrinsic aggregation in matrix and surface deterioration by encapsulant, oxygen and moisture. The LMS composite has therefore maintained large extent luminescent properties of QDs, espe-cially for the high quantum efficiency. Moreover, the fabricated white light emitting diode (WLED) utilizing LMS and YAG:Ce yellow phosphor has demonstrated excellent light performance with color coordinates around (x = 0.33, y = 0.33), correlated color temperature between 5100 and 5500 K and color rendering index of Ra = 90, R9 = 95. The luminous efficiency of the WLED has reached up to a new record of 142.5 lm/W at 20 mA. LMS provide a promising way to practically apply QDs in lightings and displays with high efficiency as well as high stability.

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