Scattering Nanoparticles-Induced Reflection Effect for Enhancing Optical Efficiency of Inverted Quantum Dots-Light-Emitting Diodes Combined With the Centrifugation Technique

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Zong-Tao Li ◽  
Jia-Yong Liang ◽  
Jia-Sheng Li ◽  
Jie-Xin Li ◽  
Yong Tang
Keyword(s):  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Columnar Structure ◽  
Luminous Flux ◽  
Equilibrium Geometry ◽  
Reflection Effect ◽  
Optical Efficiency ◽  
Promising Alternative ◽  
Light Emitting ◽  
Centrifugation Technique

Abstract Inverted packaging structure is a promising alternative for thermal isolation between light-emitting diode (LED) chips and quantum dot (QD) converters with effective heat dissipation. However, serious reflection loss occurs at the lead frame owing to the inverted bonding of LED chips. In this study, the scattering nanoparticles-induced reflection effect has been developed to enhance the optical efficiency of inverted QD-LEDs combined with the centrifugation technique. The strong back-scattered effect of boron nitride (BN) nanoparticles with a thin columnar structure is chosen for reflection enhancement according to the ray-tracing and finite different time-domain simulations. Furthermore, a centrifugation technique is introduced to control the equilibrium geometry of the BN-incorporating reflector (BNR) by changing the centrifugal speed. Results indicate that the luminous flux of inverted QD/BNR-LEDs using the optimized concave BNR structure largely increases by 82.8% compared with reference inverted QD-LEDs. The great enhancement is attributed to the light concentrated effect of the concave geometry and the strong diffusion reflection ability of BN scattering nanoparticles. Consequently, the smart design on reflection properties of inverted QD-LEDs is critical for achieving high optical performances.

scholarly journals In Vitro Effect of Photodynamic Therapy with Different Lights and Combined or Uncombined with Chlorhexidine on Candida spp.

Pharmaceutics ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1176
Author(s):  
Vanesa Pérez-Laguna ◽  
Yolanda Barrena-López ◽  
Yolanda Gilaberte ◽  
Antonio Rezusta
Keyword(s):  
Photodynamic Therapy ◽  
Light Emitting Diode ◽  
Antimicrobial Effect ◽  
Photodynamic Treatment ◽  
Candida Spp ◽  
Promising Alternative ◽  
Light Emitting ◽  
Colony Forming Units ◽  
Vitro Effect

Candidiasis is very common and complicated to treat in some cases due to increased resistance to antifungals. Antimicrobial photodynamic therapy (aPDT) is a promising alternative treatment. It is based on the principle that light of a specific wavelength activates a photosensitizer molecule resulting in the generation of reactive oxygen species that are able to kill pathogens. The aim here is the in vitro photoinactivation of three strains of Candida spp., Candida albicans ATCC 10231, Candida parapsilosis ATCC 22019 and Candida krusei ATCC 6258, using aPDT with different sources of irradiation and the photosensitizer methylene blue (MB), alone or in combination with chlorhexidine (CHX). Irradiation was carried out at a fluence of 18 J/cm2 with a light-emitting diode (LED) lamp emitting in red (625 nm) or a white metal halide lamp (WMH) that emits at broad-spectrum white light (420–700 nm). After the photodynamic treatment, the antimicrobial effect is evaluated by counting colony forming units (CFU). MB-aPDT produces a 6 log10 reduction in the number of CFU/100 μL of Candida spp., and the combination with CHX enhances the effect of photoinactivation (effect achieved with lower concentration of MB). Both lamps have similar efficiencies, but the WMH lamp is slightly more efficient. This work opens the doors to a possible clinical application of the combination for resistant or persistent forms of Candida infections.

Reliability of High-Power Light Emitting Diode Attached With Different Thermal Interface Materials

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Xin Li ◽  
Xu Chen ◽  
Guo-Quan Lu
Keyword(s):  
High Power ◽  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Temperature Cycling ◽  
Fluorescent Light ◽  
Light Sources ◽  
Light Emitting ◽  
Die Attach ◽  
Nanosilver Paste ◽  
Interconnection Material

As a solid electroluminescent source, white light emitting diode (LED) has entered a practical stage and become an alternative to replace incandescent and fluorescent light sources. However, due to the increasing integration and miniaturization of LED chips, heat flux inside the chip is also increasing, which puts the packaging into the position to meet higher requirements of heat dissipation. In this study, a new interconnection material—nanosilver paste is used for the LED chip packaging to pursue a better optical performance, since high thermal conductivity of this material can help improve the efficiency of heat dissipation for the LED chip. The bonding ability of this new die-attach material is evaluated by their bonding strength. Moreover, high-power LED modules connected with nanosilver paste, Sn3Ag0.5Cu solder, and silver epoxy are aged under hygrothermal aging and temperature cycling tests. The performances of these LED modules are tested at different aging time. The results show that LED modules sintered with nanosilver paste have the best performance and stability.

Thermal Analysis of High Power Light Emitting Diodes Package

2011 ◽  
Vol 687 ◽  
pp. 215-221
Author(s):  
Yuan Yuan Han ◽  
Hong Guo ◽  
Xi Min Zhang ◽  
Fa Zhang Yin ◽  
Ke Chu ◽  
...  
Keyword(s):  
Finite Element Method ◽  
High Power ◽  
Thermal Field ◽  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Convective Heat Exchange ◽  
Input Power ◽  
Junction Temperature ◽  
Original Structure ◽  
Light Emitting

With increasing of the input power of the chips in light emitting diode (LED)， the thermal accumulation of LEDs package increases. Therefore solving the heat issue has become a precondition of high power LED application. In this paper, finite element method was used to analyze the thermal field of high power LEDs. The effect of the heatsink structure on the junction temperature was also investigated. The results show that the temperature of the chip is 95.8°C which is the highest, and it meets the requirement. The conductivity of each component affects the thermal resistance. Convective heat exchange is connected with the heat dissipation area. In the original structure of LEDs package the heat convected through the substrate is the highest, accounting for 92.58%. Three heatsinks with fin structure are designed to decrease the junction temperature of the LEDs package.

scholarly journals Analysis of Electric Power Quantities of Road LED Luminaires under Sinusoidal and Non-Sinusoidal Conditions

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1109
Author(s):  
Roman Sikora ◽  
Przemysław Markiewicz
Keyword(s):  
Supply Voltage ◽  
Light Emitting Diode ◽  
Luminous Flux ◽  
Laboratory Measurements ◽  
Electrical Parameters ◽  
Light Emitting ◽  
Road Lighting ◽  
Legal Provisions ◽  
Acceptable Range ◽  
Deformation Level

The paper presents the results of laboratory tests concerning the measurements of electrical parameters of road lighting luminaires. These measurements were focused on determining the dependence of the electrical parameters of the luminaires versus the changes of the RMS (Root Mean Square) value of the supply voltage and the level of disturbances in the supply voltage. The basic electrical parameters for light-emitting diode (LED) luminaires were analysed with the option of luminous flux adjustment if it existed. During the laboratory measurements, the luminaires were powered from the Agilent 6834B distorted voltage generator within the assumed acceptable range of the changes in the deformation level resulting from the applicable legal provisions for the reproduction of actual power supply conditions.

scholarly journals Dispensing Technology of 3D Printing Optical Lens with Its Applications

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3118 ◽  
Author(s):  
Fang-Ming Yu ◽  
Ko-Wen Jwo ◽  
Rong-Seng Chang ◽  
Chiung-Tang Tsai
Keyword(s):  
Solar Cells ◽  
Light Emitting Diode ◽  
Contact Angles ◽  
Luminous Flux ◽  
Photoelectric Conversion Efficiency ◽  
Fluid Viscosity ◽  
Photoelectric Conversion ◽  
Uv Curable ◽  
Lens Array ◽  
Light Emitting

Current 3D printed lens technology faces reduced efficiency due to stepped and stacked lens surfaces. This research employs a faster jet dispensing method which reduces these issues. It uses UV-curable material and merges droplets before they are cured to obtain very smooth lens surfaces without any post-processing and without manufacturing a mold for lens structures. This technology can be applied to lens manufacturing in a variety of products, especially in the form of arrays, saving development time and reducing cost. Two experiments of LED (Light-emitting diode) lens and solar cell lens array mask implementations are presented to demonstrate the power of the method. Furthermore, this study analyzes the effect of different contact angles created by jet dispensing technology, including a detailed exploration of fluid viscosity and tooling heating parameters. Our results show that the LED lens can be manufactured to increase the luminous flux of large angles. Furthermore, the lens array mask for solar cells can be manufactured to reduce sunlight reflection and increase secondary refraction, which enables solar cells to achieve higher photoelectric conversion efficiency and to increase their power generation up to 4.82%.

scholarly journals The Effect of Different Filament Arrangements on Thermal and Optical Performances of LED Bulbs

2020 ◽  
Vol 10 (4) ◽  
pp. 1373
Author(s):  
Wei Wang ◽  
Jun Zou ◽  
Qiaoyu Zheng ◽  
Yuefeng Li ◽  
Bobo Yang ◽  
...  
Keyword(s):  
Thermal Cycle ◽  
Gas Flow ◽  
Performance Test ◽  
Light Emitting Diode ◽  
Luminous Flux ◽  
Junction Temperature ◽  
Test Results ◽  
Light Emitting ◽  
Three Samples ◽  
Simulation Results

The influences on thermal and optical performances of light emitting diode (LED) bulbs with three different filament arrangements are investigated in detail. The average junction temperature, temperature of the surface of the bulb, and luminous flux of three samples all increased with increasing power. The thermal performance test results show that between the average junction, temperature and power were linear. The junction temperatures of the three samples at a power of 3.5 W were 102.48, 98.46, and 88.88 °C. The optical performance test results revealed that the luminous flux and efficiency in the two vertical filament arrangements were closely related to each other and higher than that of the horizontal filament arrangement. A numerical model of LED filament bulbs was established by the Floefd 17.2 software for analyzing the temperature distribution of the cross section and the gas flow path inside the bulb. The simulation results illustrated that the average temperatures of three samples were 105.88, 101.83, and 96.12 °C. Additionally, the gas flow inside the bulb of the two vertical filament arrangements was subject to forming a thermal cycle during operation work more than that of the horizontal filament arrangement. As a result, the flexible spiral LED filament bulb is feasible as a new light source.

scholarly journals Optimization and scale-up of an LED-illuminated microalgal photobioreactor for wastewater treatment

2019 ◽  
Vol 80 (12) ◽  
pp. 2352-2361
Author(s):  
L. M. L. Silva ◽  
A. F. Santiago ◽  
G. A. Silva ◽  
A. L. P. Castro ◽  
L. S. Bastos ◽  
...  
Keyword(s):  
Organic Matter ◽  
Wastewater Treatment ◽  
Wastewater Treatment Plants ◽  
Light Emitting Diode ◽  
Scale Up ◽  
Operating Time ◽  
Luminous Flux ◽  
Light Emitting ◽  
Operational Conditions ◽  
Nitrogen Phosphorus

Abstract The use of light-emitting diode (LED)-illuminated photobioreactors with microalgae has been extensively studied for wastewater treatment. Most studies have used isolated microalgae species; however, this practice does not match the reality of conditions in wastewater treatment plants. Operational conditions that promote greater growth of algal biomass and that remove pollutants most effectively are disputed in the literature. In this context, LED-illuminated photobioreactors with microalgae were evaluated using multivariate analysis in order to optimize removal of pollutants (nitrogen, phosphorus, and carbonaceous organic matter). Three variables were evaluated: operating time, LED wavelength, and luminous flux intensity. A microalgae consortium was used in the photobioreactor. In addition to the LED-illuminated photobioreactors, control photobioreactors illuminated by sunlight were also operated. Using the results obtained in the optimization, a scaled-up reactor approximately 8.5 times larger in volume was operated to evaluate if the behavior would be maintained. The best operational conditions for the removal of pollutants were observed in LED-illuminated photobioreactors operated under a light intensity of 700 μmol·m−2s−1 for 15 days. Under these conditions, it was possible to remove 89.97% of carbonaceous organic matter, 86.50% of nitrogen, and 30.64% of phosphorus. The scaled-up photobioreactor operated with similar performance.

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