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Overhead supplemental far-red light stimulates tomato growth under intra-canopy lighting with LEDs
摘要： Far-red (FR) light regulates phytochrome-mediated morphological and physiological plant responses. This study aims to investigate how greenhouse tomato morphology and production response to different durations of FR light during daytime and at the end of day (EOD). High-wire tomato plants were grown under intra-canopy lighting consisting of red (peak wavelength at 640 nm) and blue (peak wavelength at 450 nm) light-emitting diodes (LEDs) with photosynthetic photon flux density (PPFD) of 144 μmol m–2 s–1 at 10 cm away from the lamps, and combined with overhead supplemental FR light (peak wavelength at 735 nm) with PPFD of 43 μmol m–2 s–1 at 20 cm below the lamps. Plants were exposed to three durations of FR supplemental lighting including: 06:00–18:00 (FR12), 18:00–19:30 (EOD-FR1.5), 18:00–18:30 (EOD-FR0.5), and control that without supplemental FR light. The results showed that supplemental FR light significantly stimulated stem elongation thereby resulting in longer plants compared with the control. Moreover, FR light altered leaf morphology toward higher leaf length/width ratio and larger leaf area. The altered plant architecture in FR supplemented plants led to a more homogeneous light distribution inside the canopy. Total plant biomass was increased by 9–16% under supplemental FR light in comparison with control, which led to 7–12% increase in ripe fruit yield. Soluble sugar content of the ripe tomato fruit was slightly decreased by longer exposure of the plants to FR light. Dry matter partitioning to different plant organs were not substantially affected by the FR light treatments. No significant differences were observed among the three FR light treatments in plant morphology as well as yield and biomass production. We conclude that under intra-canopy lighting, overhead supplemental FR light stimulates tomato growth and production. And supplementary of EOD-FR0.5 is more favorable, as it consumes less electricity but induces similar effects on plant morphology and yield.
关键词： intro-canopy lighting,morphology,far-red light,LEDs,yield,Solanum lycopersicum
更新于2025-09-12 10:27:22
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Tetrahedral amorphous carbon prepared filter cathodic vacuum arc for hole transport layers in perovskite solar cells and quantum dots LEDs
摘要： In this study, we demonstrated the feasibility of using tetrahedral amorphous carbon (ta-C) films coated through the filtered cathodic vacuum arc (FCVA) process as a hole transport layer (HTL) for perovskite solar cells (PSCs) and quantum dots light-emitting diodes (QDLEDs). The p-type ta-C film has several remarkable features, including ease of fabrication without the need for thermal annealing or any other post-treatment, reasonable electrical conductivity, optical transmittance, good chemical stability, and a high work function. Therefore, we present a simple and effective method to improve the performance of PSCs and QDLEDs by applying ta-C films as a HTL. X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy examinations show that the electrical properties (sp3/sp2 hybridized bond) and work function of the ta-C HTL are appropriate for PSCs and QDLEDs. In addition, in order to correlate the performance of the devices, the optical, surface morphological, and structural properties of the FCVA-grown ta-C films with different thicknesses (5 ~ 20 nm) deposited on the ITO anode are investigated in detail. The optimized ta-C film with a thickness of 5 nm deposited on the ITO anode had a sheet resistance 10.33 Ohm/square, a resistivity of 1.34 × 10-4 Ohm-cm, and an optical transmittance of 88.97%. Compared to the reference PSC with p-NiO HTL, the PSC with 5 nm thick ta-C HTL yielded a higher power conversion efficiency (PCE, 10.53%) due to its improved fill factor. Further, performance of QDLEDs with 5 nm thick ta-C hole injection layers (HIL) showed better than performance of QDLEDs with different ta-C thicknesses. It is concluded that FCVA grown ta-C films have the potential to serve as HTL and HIL in next-generation PSCs and QDLEDs.
关键词： Perovskite solar cells,Hole transport layer (HTL),Quantum dots LEDs,Tetrahedral amorphous carbon (ta-C) film,Hole injection layer (HIL)
更新于2025-09-12 10:27:22
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[IEEE 2019 25th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Lecco, Italy (2019.9.25-2019.9.27)] 2019 25th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Investigation of Thermomechanical Local Stress Induced in Assembled GaN LEDs
摘要： Bonding of LEDs on substrates by soldering or sintering induce stresses in the LEDs. Raman spectroscopy is employed to investigate the local stress. Nine blue emitting gallium nitride (GaN) LEDs were first investigated at room temperature before the bonding process. Then, two LEDs were reflow soldered on Al-IMS with ENIG metallization and four LEDs were soldered on Cu substrate using 25 μm AuSn preform. Three LEDs were sintered under pressureless sintering conditions on Cu substrate using an Ag sinter paste. All assemblies were investigated between -50 °C and 180 °C. The change in position of the GaN Raman band E2(high) at ca. 568 cm-1 was used to characterise the thermomechanical stress. The obtained values are in the MPa order of magnitude and allow us to conclude that the dielectric layer of the Al-IMS relaxes the stress very efficiently. Moreover, the samples prepared via Ag-sintering show a reduced stress, which indicate that the stress is relaxed by the soft and ductile property of silver.
关键词： sintering,thermomechanical stress,Raman spectroscopy,soldering,GaN LEDs
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - St. Petersburg, Russia (2019.10.17-2019.10.18)] 2019 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Optimization of Spectral Characteristics of the Controlled Color-Dynamic Surgical Light Source for Visualization of Organs and Tissues of Laboratory Animals
摘要： Modern LED light sources have many advantages for operational lighting. They make it possible to choose the optimal type of lighting for the surgeon during operations on certain organs and systems. The study was aimed at experimental selection of lighting parameters for various organs in vivo in normal and pathological conditions using a controlled color-dynamic LED lamp. The results showed that specific spectral parameters of lighting are necessary for certain types of organs and tissues; color and light balance adjusting improves the contrast visualization of individual tissues relative to each other. This work is the initial stage of creation of a special atlas of light source parameters for visualization of organs and tissues during surgical interventions with the use of controlled color-dynamic surgical light source.
关键词： contrast visualization of biological tissues,controlled semiconductor light sources,LEDs,surgical lighting,biomedical optical imaging,color dynamic parameters
更新于2025-09-12 10:27:22
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Modulation of Growth Kinetics of Vacuum-Deposited CsPbBr <sub/>3</sub> Films for Efficient Light-Emitting Diodes
摘要： Due to its excellent optical properties and good stability, all-inorganic halide perovskite CsPbX3 (X=I, Br, Cl) has been attracting interest for use in light-emitting diodes (LEDs). One challenge is improving the efficacy of the spatial confinement of excitons for higher luminescence efficiency. Here, we present a simple yet very effective strategy to form fine-grain-structured CsPbBr3 polycrystalline films prepared by thermal co-evaporation. The strategy involves controlling growth kinetics by adjusting the deposition flux which, along with growth temperature, determines the nucleation rate and therefore eventual grain structure. A correlation between deposition flux and average grain size was noted except for a very large deposition flux when there were large hillocks, which we attributed to the peculiar growth behavior of PbBr2 films. The growth conditions that produced a nano-scale grain structure and textured orientations without large hillocks also resulted in the highest luminescence efficiency as we anticipated. With the optimized CsPbBr3 light emitters, we demonstrate a green light-emitting (at 524 nm) LED with a maximum current efficiency of 1.07 cd/A and an extremely narrow electroluminescence spectrum of 18 nm, a result that highlights the potential of vacuum-processed CsPbBr3 films for high efficiency LEDs.
关键词： Light-emitting Diodes,Thermal co-evaporation,Perovskites,Vacuum deposition,LEDs,CsPbBr3
更新于2025-09-12 10:27:22
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Analysis of electroluminescence spectra from high optical-power density forward-biased silicon-led in standard CMOS technology
摘要： A Si-LED with high-power density p+-n junction and wedge-shaped electrodes was fabricated by standard complementary metal oxide-semiconductor (CMOS) process, and its electroluminescence (EL) spectra were measured at different forward currents. By studying the EL spectra, two interesting phenomena were found. One was that the main peak of EL spectra transited from long wavelength (1135 nm) to short wavelength (1078 nm) along with the forward current increased. The other was that two light emission peaks with energy larger than band gap (Eg) were observed. For the first time, reasonable explanations to the two phenomena were given. Here, the peak shift is attributed to that, with forward current increased, the electron-hole pair recombination of the bound excitons without assist of phonons, increases faster than that of those bound or free excitons with assist of phonons. And the existence of two energy-high light emission peaks is resulted from that, under strong electric field, hot holes absorb one or two phonons from the crystal lattice and then recombine with electrons in conduction band.
关键词： Wedge-shaped pinpoint electrode,CMOS standard technology,Electroluminescence (EL) spectra,Silicon-based light-emitting devices (Si-LEDs),Strong electric field
更新于2025-09-12 10:27:22
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Investigation of enhanced far-red emitting phosphor GdAlO3:Mn4+ by impurity doping for indoor plant growth LEDs
摘要： Phytochrome is indispensable for plant growth, which can absorb light useful for sprout, blossom, fruits. Generally, Phytochrome PR absorbs red light and Phytochrome PFR absorbs far-red light. The emission of Mn4+ doped GdAlO3 is situated in far-red light region. Herein, GdAlO3:Mn4+, Mg2+(GAL:Mn4+, Mg2+) phosphors were successfully synthesized via sol-gel method and the crystalline structure and luminescent properties were investigated systematically. Impressively, the emission intensity of GAL: Mn4+ phosphors was raised by Mg2+ and Ge4+ doping, and the mechanism of improved luminescence was also discussed. Depending on photoluminescence excitation and photoluminescence spectroscopy, the crystal field strength of the GdAlO3 host was calculated. In addition, excellent color purity and good thermal stability were found in Mg2+ co-doped GdAlO3:Mn4+ phosphors. Furthermore, the luminescence spectra of GAL: Mn4+, Mg2+ phosphor was agreed well with the absorption of Phytochrome PFR, which convincingly confirmed that Mg2+ co-doped GdAlO3:Mn4+ phosphors show promise in indoor plant growth LEDs.
关键词： indoor plant growth LEDs,far-red-emitting,Phytochrome PFR,Mn4+ luminescence
更新于2025-09-12 10:27:22
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European Microscopy Congress 2016: Proceedings || Analytical electron microscopy characterization of light-emitting diodes based on ordered InGaN nanocolumns
摘要： Self-assembled nanocolumns (NCs) with InGaN/GaN disks constitute an alternative to conventional light emitting diodes (LED) planar devices [1]. However, their efficiency and reliability are hindered by a strong dispersion of electrical characteristics among individual nanoLED. Polychromatic emission derives from an inhomogeneous distribution of indium concentration due to the inherent tendency of InGaN alloys to develop composition fluctuations as a function of the polarity of the growth crystallographic planes [2]. The recent development of selective area growth of NCs by molecular beam epitaxy has allowed the achieving of highly homogeneous and controllable GaN/InGaN NCs with improved crystalline quality and higher control over the indium distribution [3]. In this work, we present the characterization performed on LEDs based on ordered NCs with InGaN active disks (figure 1). The detailed structural characterization of the nanostructures has been performed by scanning transmission electron microscopy (STEM) carried out on an aberration-corrected JEOL-JEMARM200 microscope. High crystal quality of the NCs is set by the analysis of atomically-resolved high angle annular dark field (HAADF) images. The indium distribution within the InGaN disks is studied by EDS elemental mapping while the polarity of the semiconductor NCs is followed by locating the nitrogen atomic columns in annular bright field (ABF) images while (figure2). Direct correlation of the optical and structural properties on a nanometer-scale was achieved using low temperature cathodoluminescence (CL) spectroscopy in an FEI STEM Tecnai F20 [4].
关键词： nanowires,EDS,annular bright field,InGaN,LEDs,atomic-resolution STEM
更新于2025-09-12 10:27:22
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Ultraefficient Green LEDs Using Quantum Dots in Liquid Matrix
摘要： Green spectral range, which has the highest human eye sensitivity, is one of the most fundamental colors in lighting and display. Quantum dots (QDs) offer exceptional optical properties including high quantum yield (QY), strong absorption, and narrow emission linewidths for efficient green-emitting diodes. In this article, we demonstrated QD-based light-emitting diodes (QD-LEDs) that operate at a luminous efficiency (LE) level of 95 lumens per electrical watt, the luminous efficacy of optical radiation of 409 lumens per optical watt, and external quantum efficiency (EQE) of 23.3% in the green spectral region. For that, we synthesized 1-octanethiol-capped CdSe/ZnS QDs with an absolute QY of 91% and integrated them in a liquid matrix that allows conservation of the QD efficiency in device architecture. Our simulations were in agreement with the performance of the fabricated QD-LEDs, and they showed that the QD-LEDs can be further improved to reach LE levels over 250 lm/W.
关键词： light-emitting diodes (LEDs),luminous efficiency (LE),liquid-state integration,quantum dots (QDs),External quantum efficiency (EQE)
更新于2025-09-12 10:27:22
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Influence of spectral intensity and quality of LED lighting on photoacclimation, carbon allocation and high-value pigments in microalgae
摘要： Tailoring spectral quality during microalgal cultivation can provide a means to increase productivity and enhance biomass composition for downstream biorefinery. Five microalgae strains from three distinct lineages were cultivated under varying spectral intensities and qualities to establish their effects on pigments and carbon allocation. Light intensity significantly impacted pigment yields and carbon allocation in all strains, while the effects of spectral quality were mostly species-specific. High light conditions induced chlorophyll photoacclimation and resulted in an increase in xanthophyll cycle pigments in three of the five strains. High-intensity blue LEDs increased zeaxanthin tenfold in Rhodella sp. APOT_15 relative to medium or low light conditions. White light however was optimal for phycobiliprotein content (11.2 mg mL?1) for all tested light intensities in this strain. The highest xanthophyll pigment yields for the Chlorophyceae were associated with medium-intensity blue and green lights for Brachiomonas submarina APSW_11 (5.6 mg g?1 lutein and 2.0 mg g?1 zeaxanthin) and Kirchneriella aperta DMGFW_21 (1.5 mg g?1 lutein and 1 mg g?1 zeaxanthin), respectively. The highest fucoxanthin content in both Heterokontophyceae strains (2.0 mg g?1) was associated with medium and high white light for Stauroneis sp. LACW_24 and Phaeothamnion sp. LACW_34, respectively. This research provides insights into the application of LEDs to influence microalgal physiology, highlighting the roles of low light on lipid metabolism in Rhodella sp. APOT_15, of blue and green lights for carotenogenesis in Chlorophyceae and red light-induced photoacclimation in diatoms.
关键词： Carbon allocation,Phycobiliproteins,Microalgal physiology,LEDs,Carotenoids
更新于2025-09-12 10:27:22