scholarly journals Recycling of Gallium from End-of-Life Light Emitting Diodes

2017 ◽  
Vol 62 (2) ◽  
pp. 1161-1166 ◽  
Author(s):  
S. Nagy ◽  
L. Bokányi ◽  
I. Gombkötő ◽  
T. Magyar
Keyword(s):  
End Of Life ◽  
Circular Economy ◽  
Light Emitting Diodes ◽  
Chemical Activation ◽  
Liquid Crystal Displays ◽  
High Energy ◽  
High Energy Density ◽  
Light Emitting ◽  
Recycling Technology ◽  
Chemical Techniques

AbstractNowadays Light Emitting Diodes (LEDs) are widely utilized. They are applied as backlighting in Liquid Crystal Displays (LCD) and TV sets or as lighting equipments in homes, cars, instruments and street-lightning. End of life equipments are containing more and more LEDs. The recovery of valuable materials – such as Ga, Au, Cu etc. – from the LEDs is essential for the creating the circular economy. First task is the development of a proper recycling technology. Most of the researchers propose fully chemical or thermal-chemical pathway for the recycling of LEDs.In the meantime our approach based on the thorough investigation of the structure and composition of LEDs, and shown in this paper, is the combination of mechanical and chemical techniques in order to recover more valuable products, as well as to facilitate the mass transfer. Our laboratory scale experiments are introduced, the final aim of which is Ga recovery in accordance with our above approach. It was experimentally proved that the LED chips contain Ga and can be recovered by mechanical processes along with copper-product. Ga is presented on the surface of the chips in GaN form. Mechano-chemical activation in high energy density stirred medium mill and the following acidic leaching resulted in the enrichment of 99.52% of gallium in the pregnant solution.

Highly Efficient Phosphorescent Green Organic Light-Emitting Diodes with High Energy Gap Host Materials

2010 ◽  
Vol 530 (1) ◽  
pp. 83/[239]-90/[246]
Author(s):  
Hoe Min Kim ◽  
Ji Hyun Seo ◽  
Kum Hee Lee ◽  
Hyun Ju Kang ◽  
Seung Soo Yoon ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Energy Gap ◽  
High Energy ◽  
Organic Light Emitting Diodes ◽  
Light Emitting ◽  
Highly Efficient ◽  
Organic Light ◽  
Host Materials

Electroluminescence Properties of InGaN/AlGaN/GaN Light Emitting Diodes with Quantum Wells

1998 ◽  
Vol 537 ◽  
Author(s):  
A.E. Yunovich ◽  
V.E. Kudryashov ◽  
A..N. Turkin ◽  
A.N. Kovalev ◽  
F.I. Manyakhin
Keyword(s):  
Quantum Wells ◽  
Large Scale ◽  
Light Emitting Diodes ◽  
Spectral Band ◽  
High Energy ◽  
Model Fit ◽  
Multiple Quantum ◽  
Light Emitting ◽  
Wide Range ◽  
Tunnel Effects

AbstractElectroluminescence spectra of light-emitting diodes based on InGaN/AlGaN/GaN heterostructures with single and multiple quantum wells (QWs) are analyzed by models of radiative recombination in 2D-structures with band tails. Equations of the model fit spectra quite good in a wide range of currents. Parameters of the fit are discussed and compared for single and multiple QWs. Tunnel effects play a sufficient role in blue LEDs with single QWs at low currents; they can be neglected in LEDs with multiple QWs. A new spectral band was detected at the high energy side of the spectra of green LEDs with multiple QWs; it is attributed with large scale inhomogenities of In distribution in InGaN QWs.)

scholarly journals Design and Preparation of Biomass-Derived Carbon Materials for Supercapacitors: A Review

2018 ◽  
Vol 4 (4) ◽  
pp. 53 ◽  
Author(s):  
Yang Liu ◽  
Jiareng Chen ◽  
Bin Cui ◽  
Pengfei Yin ◽  
Chao Zhang
Keyword(s):  
Chemical Activation ◽  
High Energy ◽  
High Energy Density ◽  
Nanoporous Structure ◽  
Clear Understanding ◽  
Structure Property ◽  
Carbon Yield ◽  
Research Attention ◽  
Elemental Compositions ◽  
Supercapacitor Applications

The synthesis and application of biomass-derived carbon in energy storage have drawn increasing research attention due to the ease of fabrication, cost-effectiveness, and sustainability of the meso/microporous carbon produced from various biological precursors, including plants, fruits, microorganisms, and animals. Compared to the artificial nanostructured carbons, such as fullerene, carbon nanotube and graphene, the biomass-derived carbons may obtain superior capacitance, rate performance and stability in supercapacitor applications ascribing to their intrinsic nanoporous and hierarchical structures. However, challenges remain in processing techniques to obtain biomass-derived carbons with high carbon yield, high energy density, and controllable graphitic microstructures, which may require a clear understanding over the chemical and elemental compositions, and the intrinsic microstructural characteristics of the biological precursors. Herein we present comprehensive analyses over the impacts of the chemical and elemental compositions of the precursors on the carbon yield of the biomass, as well as the mechanism of chemical activation on the nanoporous structure development of the biomass-derived carbons. The structure–property relationship and functional performance of various biomass-derived carbons for supercapacitor applications are also discussed in detail and compared. Finally, useful insights are also provided for the improvements of biomass-derived carbons in supercapacitor applications.

scholarly journals Growing lettuce under multispectral light-emitting diodes lamps with adjustable light intensity

2017 ◽  
Vol 11 ◽  
Author(s):  
Giacomo Tosti ◽  
Paolo Benincasa ◽  
Rossano Cortona ◽  
Beatrice Falcinelli ◽  
Michela Farneselli ◽  
...  
Keyword(s):  
Light Intensity ◽  
Conversion Efficiency ◽  
Light Emitting Diodes ◽  
Biomass Conversion ◽  
High Energy ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Emitting ◽  
Light Spectra ◽  
Use Efficiency

Light-Emitting Diodes (LEDs) technology offers vast possibilities in plant lighting due to its ability to mix different light frequencies, high energy use efficiency and low heat production combined to long lifespan. In particular, the combined effect of the Blue:Red (B:R) ratio and other frequencies in the central part of the PAR spectrum (CGA, <em>i.e.</em> cyan, green and amber) may be very important, though literature information is scarce. In this paper, the effects of six light spectra from LED technology were tested, <em>i.e.</em>: (i) B:R=0.82 (<em>i.e.</em> similar to sunlight) with CGA (treatment T0), (ii) B:R=0.82 without CGA (T1), (iii) red prevalence (B:R=0.25) without CGA (T2), (iv) blue prevalence (B:R=4) without CGA (T3), (v) red prevalence with CGA (T4) and (vi) blue prevalence with CGA (T5). The experiment was carried out in a walk-in climatic chamber with controlled temperature and relative humidity and an incident PAR photon flux density (PFD) of 300 μmol m<sup>–2</sup> s<sup>–1</sup> (14/10 light/dark photoperiod), generated by multispectral LED lamps with adjustable light intensity. Smooth leaved lettuce (Lactuca sativa L. cv Gentilina) was used as the test plant and biomass yield (DW, g m<sup>–2</sup>), LAI, soil coverage proportion (SC%), energy-biomass conversion efficiency (E-BCE, kWh g<sup>–1</sup>) and Radiation Use Efficiency (RUE, g mol<sup>–1</sup> photons) were determined. Treatments with red predominance (T2 and T4) showed the highest SC% rates, while those with blue predominance (T3 and T5) showed the lowest. Light spectrum also affected leaf size (<em>i.e. </em>mean leaf area). The highest DW and RUE were observed in T2 and T4, followed by T0, while biomass in T3 and T5 was significantly lower (similar to T1). LAI values were generally high, but treatments with blue predominance showed the lowest LAI values (both with or without CGA). The introduction of intermediate wavelengths (green, cyan and amber) did not bring about significant improvement in DW or RUE, but resulted in reduced energy-biomass conversion efficiency, mainly due to lower architectural efficiency of the CGA LEDs. Future research should clarify how to optimise the light spectra according to the crop growth phases. The adoption of spectra promoting fast growth is fundamental in the early growth, while the use of spectra maximising yield quality may be more important later on.

Junction Temperature Measurements in Deep-UV Light-Emitting Diodes

2004 ◽  
Vol 831 ◽  
Author(s):  
Y. Xi ◽  
J.-Q. Xi ◽  
Th. Gessmann ◽  
J. M. Shah ◽  
J. K. Kim ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Energy Gap ◽  
Uv Light ◽  
Accurate Method ◽  
High Energy ◽  
Junction Temperature ◽  
Forward Voltage ◽  
Light Emitting ◽  
Thermal Paste ◽  
Carrier Temperature

ABSTRACTThe junction temperature of AlGaN/GaN ultraviolet (UV) Light-Emitting Diodes (LEDs) emitting at 295 nm is measured by using the temperature coefficients of the diode forward voltage and emission peak energy. The high-energy slope of the spectrum is explored to measure the carrier temperature. A linear relation between junction temperature and current is found. Analysis of the experimental methods reveals that the diode-forward voltage is the most accurate method (± 3 °C). A theoretical model for the dependence of the diode junction voltage (Vj) on junction temperature (T) is developed that takes into account the temperature dependence of the energy gap. A thermal resistance of 87.6 K/W is obtained with the AlGaN/GaN LED sample mounted with thermal paste on a heat sink.

Reliability potential of silicone molding compounds for LED application

2014 ◽  
Vol 2014 (1) ◽  
pp. 000258-000261 ◽  
Author(s):  
Yue Shao ◽  
Yu-chou Shih ◽  
Frank G. Shi
Keyword(s):  
Radiation Resistance ◽  
Uv Light ◽  
Light Output ◽  
High Energy ◽  
High Energy Density ◽  
Packaging Materials ◽  
Molding Compound ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Reliability Performance

As the development of light emitting devices (LEDs), integrate circuits (ICs) and concentration photovoltaic (CPV) modules towards higher density, packaging materials are facing the challenges of withstand with heat generation and high energy. Epoxy molding compound (EMC) is the latest technology for LED and solar cell package to replace PPA and PCT. However, it is well known that the thermal and radiation resistance of epoxy is limited. Recently, silicone based composites are attracting attention as ideal materials because they are insensible to high energy density and good resistance to UV light and heat. Epoxy and silicone both have reliability issues during long-term service at high temperature and high energy. Thermal and radiation degradation of reflector materials will largely affect their reflectance and their contribution to a higher light output and energy efficiency. Therefore, it is very essential to evaluate reliability performance of SMC and EMC based reflecting materials. Aging under multiple environmental conditions has generated considerable interest for evaluating the life and behavior of materials in a real environment. Radiation and thermal aging are two quite different types of aging. The combination of these two situations will cause the aging process to accelerate further. The objective of this study is to investigate the synergetic influence of thermal and radiation aging on optical performance of SMC and EMC based packaging materials. It is concluded that SMC is the preferred choice for packaging LEDs, ICs and solar cells for its superior thermal and radiation resistance.

scholarly journals Biomass-Derived Porous Carbons Derived from Soybean Residues for High Performance Solid State Supercapacitors

Molecules ◽  
2020 ◽  
Vol 25 (18) ◽  
pp. 4050 ◽  
Author(s):  
Hsiu-Ying Chung ◽  
Guan-Ting Pan ◽  
Zhong-Yun Hong ◽  
Chun-Tsung Hsu ◽  
Siewhui Chong ◽  
...  
Keyword(s):  
Solid State ◽  
Surface Area ◽  
Synergistic Effects ◽  
Chemical Activation ◽  
High Energy ◽  
High Energy Density ◽  
Bet Surface Area ◽  
Electrochemical Performances ◽  
Porous Carbons ◽  
Symmetric Supercapacitor

A series of heteroatom-containing porous carbons with high surface area and hierarchical porosity were successfully prepared by hydrothermal, chemical activation, and carbonization processes from soybean residues. The initial concentration of soybean residues has a significant impact on the textural and surface functional properties of the obtained biomass-derived porous carbons (BDPCs). SRAC5 sample with a BET surface area of 1945 m2 g−1 and a wide micro/mesopore size distribution, nitrogen content of 3.8 at %, and oxygen content of 15.8 at % presents the best electrochemical performance, reaching 489 F g−1 at 1 A g−1 in 6 M LiNO3 aqueous solution. A solid-state symmetric supercapacitor (SSC) device delivers a specific capacitance of 123 F g−1 at 1 A g−1 and a high energy density of 68.2 Wh kg−1 at a power density of 1 kW kg−1 with a wide voltage window of 2.0 V and maintains good cycling stability of 89.9% capacitance retention at 2A g−1 (over 5000 cycles). The outstanding electrochemical performances are ascribed to the synergistic effects of the high specific surface area, appropriate pore distribution, favorable heteroatom functional groups, and suitable electrolyte, which facilitates electrical double-layer and pseudocapacitive mechanisms for power and energy storage, respectively.

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