scholarly journals Investigation of a Separated Short-Wavelength Peak in InGaN Red Light-Emitting Diodes

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1123
Author(s):  
Pavel Kirilenko ◽  
Zhe Zhuang ◽  
Daisuke Iida ◽  
Martin Velazquez-Rizo ◽  
Kazuhiro Ohkawa
Keyword(s):  
Quantum Wells ◽  
Short Wavelength ◽  
Light Emitting Diodes ◽  
Red Light ◽  
Blue Shift ◽  
Light Emitting ◽  
Peak Emission Wavelength ◽  
Wavelength Emission ◽  
Main Emission Peak ◽  
Red Leds

We fabricated indium gallium nitride (InGaN) red light-emitting diodes (LEDs) with a peak emission wavelength of 649 nm and investigated their electroluminescence (EL) properties. An additional separated peak in the EL spectrum of the red LEDs at 20 mA was observed at 465 nm. This additional peak also exhibits a blue-shift with increasing currents as does the main emission peak. Using high-resolution microscopy, we observed many point-like emission spots in the EL emission images at the currents below 1 mA. However, these emission spots cannot be identified at currents above 5 mA because the red emission from quantum wells (QWs) is much stronger than that emitted by these spots. Finally, we demonstrate that these emission spots are related to the defects generated in red QWs. The measured In content was lower at the vicinity of the defects, which was regarded as the reason for separated short-wavelength emission in red InGaN LEDs.

Stress engineering for reducing the injection current induced blue shift in InGaN-based red light-emitting diodes

CrystEngComm ◽  
2021 ◽  
Author(s):  
Weizhen Yao ◽  
Lianshan Wang ◽  
Yulin Meng ◽  
Shaoyan Yang ◽  
Xianglin Liu ◽  
...  
Keyword(s):  
Sapphire Substrate ◽  
Light Emitting Diodes ◽  
Red Light ◽  
Blue Shift ◽  
Ingan Layer ◽  
Patterned Sapphire Substrate ◽  
Light Emitting ◽  
Stress Engineering ◽  
Engineering Strategy ◽  
Red Leds

Red LEDs with a small blue shift are fabricated by using a stress engineering strategy through the growth of the pre-stained InGaN layer and dual-wavelength QWs on a cone-shape patterned sapphire substrate.

scholarly journals Specific Light-Emitting Diodes Can Suppress Sporulation of Podosphaera pannosa on Greenhouse Roses

Plant Disease ◽  
2010 ◽  
Vol 94 (9) ◽  
pp. 1105-1110 ◽  
Author(s):  
A. Suthaparan ◽  
S. Torre ◽  
A. Stensvand ◽  
M. L. Herrero ◽  
R. I. Pettersen ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
White Light ◽  
Light Emitting Diodes ◽  
Dark Period ◽  
Red Light ◽  
Suppressive Effect ◽  
Continuous Illumination ◽  
Light Emitting ◽  
Dark Interval ◽  
Red Leds

When rose plants bearing colonies of Podosphaera pannosa were placed in a wind tunnel, the number of conidia trapped was directly proportional to intensity of daylight-balanced (white) light from 5 to 150 μmol m–2 s–1. Illumination of samples using blue (420 to 520 nm) light-emitting diodes (LEDs) increased the number of conidia trapped by a factor of approximately 2.7 over white light but germination of conidia under blue light was reduced by approximately 16.5% compared with conidia germination under white light. The number of conidia trapped under far-red (>685 nm) LEDs was approximately 4.7 times higher than in white light, and 13.3 times higher than under red (575 to 675 nm) LEDs, and germination was not induced compared with white light. When mildewed plants were exposed to cycles of 18 h of white light followed by 6 h of blue, red, far-red light, or darkness, light from the red LEDs reduced the number of conidia trapped by approximately 88% compared with darkness or far-red light. Interrupting the above dark period with 1 h of light from red LEDs also reduced the number of conidia trapped, while a 1-h period of light from far-red following the 1 h of light from red LEDs nullified the suppressive effect of red light. Our results indicate that brief exposure to red light during the dark interval may be as effective as continuous illumination in suppressing powdery mildew in greenhouse rose plant (Rosa × hybrida).

Design of C^NN type iridium(iii) complexes towards short-wavelength emission for high efficiency organic light-emitting diodes

RSC Advances ◽  
2016 ◽  
Vol 6 (85) ◽  
pp. 81869-81876 ◽  
Author(s):  
Xun Lu Zhang ◽  
Shao Jie Liu ◽  
Li Yuan Guo ◽  
Chuan Jun Wang ◽  
Yu Tong ◽  
...  
Keyword(s):  
Short Wavelength ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Organic Light Emitting Diodes ◽  
Light Emitting ◽  
Organic Light ◽  
Wavelength Emission

The first blue-emitting C^NN based Ir-complex was synthesized and applied to PhOLEDs, with efficiencies of 20.1% and 41.6 cd A−1.

scholarly journals Growth, Nutritional Quality, and Energy Use Efficiency of Hydroponic Lettuce as Influenced by Daily Light Integrals Exposed to White versus White Plus Red Light-emitting Diodes

HortScience ◽  
2019 ◽  
Vol 54 (10) ◽  
pp. 1737-1744 ◽  
Author(s):  
Zhengnan Yan ◽  
Dongxian He ◽  
Genhua Niu ◽  
Qing Zhou ◽  
Yinghua Qu
Keyword(s):  
Nutritional Quality ◽  
Energy Use ◽  
Light Emitting Diodes ◽  
Red Light ◽  
Dry Weight ◽  
Light Emitting ◽  
Energy Use Efficiency ◽  
White Leds ◽  
Use Efficiency ◽  
Red Leds

Few researchers examined different red light amounts added in white light-emitting diodes (LEDs) with varied daily light integrals (DLIs) for hydroponic lettuce (Lactuca sativa L.). In this study, effects of DLI and LED light quality (LQ) on growth, nutritional quality, and energy use efficiency of hydroponic lettuce were investigated in a plant factory with artificial lighting (PFAL). Hydroponic lettuce plants (cv. Ziwei) were grown for 20 days under 20 combinations of five levels of DLIs at 5.04, 7.56, 10.08, 12.60, and 15.12 mol·m−2·d−1 and four LQs: two kinds of white LEDs with red to blue ratio (R:B ratio) of 0.9 and 1.8, and two white LEDs plus red chips with R:B ratio of 2.7 and 3.6, respectively. Results showed that leaf and root weights and power consumption based on fresh and dry weights increased linearly with increasing DLI, and light and electrical energy use efficiency (LUE and EUE) decreased linearly as DLI increased. However, no statistically significant differences were found in leaf fresh and dry weights and nitrate and vitamin C contents between DLI at 12.60 and 15.12 mol·m−2·d−1. Also, no effects of LQ on leaf dry weight of hydroponic lettuce were observed at a DLI of 5.04 mol·m−2·d−1. White plus red LEDs with an R:B ratio of 2.7 resulted in higher leaf fresh weight than the two white LEDs. LUE increased by more than 20% when red light fraction increased from 24.2% to 48.6%. In summary, white plus red LEDs with an R:B ratio of 2.7 at DLI at 12.60 mol·m−2·d−1 were recommended for commercial hydroponic lettuce (cv. Ziwei) production in PFALs.

scholarly journals Growth and Carbohydrate Metabolism of Wheat Plants Grown with Red-light Emitting Diodes

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 863C-863
Author(s):  
N.C. Yorio ◽  
M. Sanwo ◽  
C.S. Brown
Keyword(s):  
Light Emitting Diodes ◽  
Starch Content ◽  
Red Light ◽  
Fold Increase ◽  
Sucrose Phosphate Synthase ◽  
Small Mass ◽  
Fluorescent Light ◽  
Light Emitting ◽  
Carbohydrate Concentration ◽  
Red Leds

Light-emitting diodes (LEDs) are a potential light source for growing plants in space flight systems because of their superior safety and reliability, small mass and volume, electrical efficiency, and longevity. To determine the influence of narrow-spectrum LEDs on plant growth and metabolism, wheat (Triticum aestivum L. `Superdwarf') plants were grown under red LEDs (peak emission 660 nm) and compared to plants grown under daylight fluorescent, red LEDs + 1% blue fluorescent light (BL), and red LEDs + 10% BL. Plants were taller, had longer flag leaves, and delayed seed development when grown under red LEDs or red LEDs + 1% BL compared to those grown with 10% BL or under daylight fluorescent. Viable seeds (290% germination) were produced in all plants regardless of the light treatment. Total dry matter (DM), head DM, and seed DM were similar in the plants grown under the four light regimes, and there were no differences in the starch content of the seeds. Starch levels were 4-times greater and sucrose levels were 2.5-times greater in leaves of plants grown under the red LEDs compared to daylight fluorescent. Daylight fluorescent leaves showed a 1.8-fold increase in sucrose phosphate synthase (SPS) activity, a regulatory enzyme of sucrose synthesis. These results indicate that wheat can be grown successfully under red LEDs, but there are differences in carbohydrate concentration and metabolism in photosynthetic tissue.

scholarly journals Recent progress in red light-emitting diodes by III-nitride materials

2021 ◽  
Author(s):  
Daisuke Iida ◽  
Kazuhiro Ohkawa
Keyword(s):  
Recent Progress ◽  
Light Emitting Diodes ◽  
Red Light ◽  
Strain Engineering ◽  
Research Field ◽  
Material System ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Highly Efficient ◽  
Red Leds

Abstract GaN-based light-emitting devices have the potential to realize all visible emissions with the same material system. These emitters are expected to be next-generation RGB displays and illumination tools. These emitting devices have been realized with highly efficient blue and green light-emitting diodes (LEDs) and laser diodes (LDs). Extending them to longer wavelength emissions remains challenging from an efficiency perspective. In the emerging research field of micro-LED displays, III-nitride red LEDs are in high demand to establish highly efficient devices like conventional blue and green systems. In this review, we describe fundamental issues in the development of red LEDs by III-nitrides. We also focus on the key role of growth techniques such as higher temperature growth, strain engineering, nanostructures, and Eu doping. The recent progress and prospect of developing III-nitride-based red light-emitting devices will be presented.

scholarly journals Enhanced Optoelectronic Performance of Yellow Light-Emitting Diodes Grown on InGaN/GaN Pre-Well Structure

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3231
Author(s):  
Xiaoyu Zhao ◽  
Zehong Wan ◽  
Liyan Gong ◽  
Guoyi Tao ◽  
Shengjun Zhou
Keyword(s):  
Quantum Wells ◽  
Stark Effect ◽  
Light Emitting Diodes ◽  
Light Output ◽  
Fold Increase ◽  
Blue Shift ◽  
Underlying Mechanism ◽  
Localized States ◽  
Multiple Quantum ◽  
Light Emitting

InGaN-based long-wavelength light-emitting diodes (LEDs) are indispensable components for the next-generation solid-state lighting industry. In this work, we introduce additional InGaN/GaN pre-wells in LED structure and investigate the influence on optoelectronic properties of yellow (~575 nm) LEDs. It is found that yellow LED with pre-wells exhibits a smaller blue shift, and a 2.2-fold increase in light output power and stronger photoluminescence (PL) intensity compared to yellow LED without pre-wells. The underlying mechanism is revealed by using Raman spectra, temperature-dependent PL, and X-ray diffraction. Benefiting from the pre-well structure, in-plane compressive stress is reduced, which effectively suppresses the quantum confined stark effect. Furthermore, the increased quantum efficiency is also related to deeper localized states with reduced non-radiative centers forming in multiple quantum wells grown on pre-wells. Our work demonstrates a comprehensive understanding of a pre-well structure for obtaining efficient LEDs towards long wavelengths.

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