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- 实验方案
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Metal-insulator-semiconductor structure for deep-ultraviolet light-emitting diodes to increase the electron injection in the cathode region
摘要： In this work, we propose using metal-insulator-semiconductor (MIS) structure on the n-AlGaN layer to reduce the contact resistance and improve the wall-plug efficiency (WPE) for AlGaN based deep ultraviolet light-emitting diodes (DUV LEDs). The thin insulator between the cathode metal and the n-AlGaN layer can share the bias, which makes the n-AlGaN layer surface less depleted and thus the MIS-type cathode structure favors the intraband tunneling effect for electrons. Moreover, the adoption of the MIS-structure aligns the electron affinity for the metal above the conduction band for the n-AlGaN layer, and this avoids the electron transport by thermionic emission. Thanks to the MIS-type cathode, we find that excellent electron transport can be obtained even if the metal with big electron affinity is used. This work also conducts an in-depth investigation into the impact of the relative dielectric constant, the bandgap, the affinity, the length and the thickness for the insulator on the electron transport and the WPE of DUV LEDs. We find that an insulator with a small dielectric constant is required for promoting the electron tunneling in the MIS-type cathode region.
关键词： Insulator,DUV LEDs,Ohmic contact,n-AlGaN,MIS structure
更新于2025-09-19 17:13:59
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From physics to fixtures to food: current and potential LED efficacy
摘要： Light-emitting diodes (LEDs) have enabled a historic increase in the conversion of electric energy to photons, but this is approaching a physical limit. The theoretical maximum efficiency occurs when all input energy is converted to energy in photosynthetic photons. Blue LEDs can be 93% efficient, phosphor-converted “whites” 76% efficient, and red LEDs 81% efficient. These improvements open new opportunities for horticultural lighting. Here we review (1) fundamental physics and efficiency of LEDs, (2) the current efficacy of LEDs, (3) the effect of spectral quality on crop yield, and (4) the potential efficacy of horticultural fixtures. Advances in the conversion of photons to yield can be achieved by optimization of spectral effects on plant morphology, which vary among species. Conversely, spectral effects on photosynthesis are remarkably similar across species, but the photons conventional (400–700 nm) may need to be modified. The upper limit of LED fixture efficacy is determined by the LED package efficacy multiplied by four factors inherent to all fixtures: thermal droop, driver (power supply) current droop, inefficiencies, and optical losses. With current LED technology, the calculations indicate efficacy limits of 3.4 μmol J?1 for white + red fixtures, and 4.1 μmol J?1 for blue + red fixtures. Adding optical protection from water and high humidity reduces these values by ~10%. We describe tradeoffs between peak efficacy and cost.
关键词： spectral quality,fixture efficacy,horticultural lighting,LEDs,photosynthetic photons
更新于2025-09-19 17:13:59
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Suppression of efficiency droop in AlGaN based deep UV LEDs using double side graded electron blocking layer.
摘要： We have envisaged and designed a novel III-V Nitride based deep ultraviolet light emitting diodes (DUV LEDs) with reasonably high efficiency at higher current density using a double-side grading in electron blocking layer (EBL). Double-side step- and linear-grading in EBL yield better performance attributable to improved hole injection, stifled electron overflow and diminished electrostatic field in the active region. The performance curves indicate that double sided linear grading in EBL has 5.63 times enhancement in power compared to the conventional LED and the efficiency droop is as low as 15% at the current density of 200 A/cm2 for the emission wavelength of ~273 nm.
关键词： Double side compositional grading,Electron Blocking Layer (EBL),Internal Quantum Efficiency (IQE),Deep Ultraviolet (DUV) LEDs
更新于2025-09-19 17:13:59
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Fabrication of flexible AlGaInP LED
摘要： Flexible light-emitting diodes (LEDs) are highly desired for wearable devices, flexible displays, robotics, biomedicine, etc. Traditionally, the transfer process of an ultrathin wafer of about 10–30 μm to a flexible substrate is utilized. However, the yield is low, and it is not applicable to thick GaN LED chips with a 100 μm sapphire substrate. In this paper, transferable LED chips utilized the mature LED manufacture technique are developed, which possesses the advantage of high yield. The flexible LED array demonstrates good electrical and optical performance.
关键词： light-emitting diodes (LEDs),performance,transfer,flexible
更新于2025-09-19 17:13:59
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[IEEE ICASSP 2020 - 2020 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) - Barcelona, Spain (2020.5.4-2020.5.8)] ICASSP 2020 - 2020 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) - The Effect of Power Allocation on Visible Light Communication Using Commercial Phosphor-Converted Led Lamp for Indirect Illumination
摘要： Visible light communication (VLC) systems should be designed to provide illumination and wireless data services simultaneously. To achieve this goal at a reasonable cost, the use of Phosphor-Converted (PC) LEDs for indirect illumination should be favored to provide a homogeneous and reliable coverage in the whole service area. Unfortunately, PC-LEDs found in the market so far have not been designed for data transmission; moreover, the response of the other (electro-)optical components of the VLC link are far from ideal. In this paper, we estimate the data rate that is feasible with VLC when indirect illumination is used. For this purpose, the end-to-end response of the VLC link is first modeled using actual measurements of the spectral power distribution of a PC-LED lamp and the ceiling reflectance. Then, different power allocation schemes are studied assuming an optical OFDM waveform. As commercial LEDs have a relatively slow time response, the equivalent VLC channel that results has strong frequency selectivity; therefore, notable data rate gains are achievable when water filling power allocation is applied.
关键词： Optical OFDM,Visible Light Communication,Illumination,Power Allocation,PC-LEDs
更新于2025-09-19 17:13:59
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A Cocktail of Multiple Cations in Inorganic Halide Perovskite towards Efficient and Highly Stable Blue Light-Emitting Diodes
摘要： Blue-emitting materials and their light-emitting diodes (LEDs) are always challenging in the application of lighting and display. Recently, perovskite LEDs (PeLEDs) with efficient and stable green/red emission have made great progress, where external quantum efficiency (EQE) over 20% has been reached. However, it is still a big challenge to realize stable blue PeLEDs with high efficiency mainly due to the poor film quality and unreasonable device structure. Herein, a cocktail strategy, that is, multi-cation (Cs/Rb/FA/PEA/K)Pb(Cl/Br)3 is demonstrated to improve both the efficiency and stability of blue PeLEDs. Combined with the “insulator-perovskite-insulator” structure, PeLEDs based on multi-cation (Cs/Rb/FA/PEA/K)Pb(Cl/Br)3 perovskite film show maximum EQE of 2.01% and maximum luminance of 4015 cd/m2 at 484 nm. More importantly, the device exhibits robust durability, and its half-lifetime is over 300 min under continuous operation. The multi-cation strategy could open up new avenue to design new blue-emitting materials for high-performing PeLEDs.
关键词： Stability,Multi-cation strategy,Perovskite LEDs,Blue-emitting materials,Efficiency
更新于2025-09-19 17:13:59
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Spectrally Tunable and Stable Electroluminescence Enabled by Rubidium Doping of CsPbBr <sub/>3</sub> Nanocrystals
摘要： Perovskite nanocrystals exhibit high photoluminescence quantum yields (PLQYs) and tunable bandgaps from ultraviolet to infrared. However, blue perovskite light-emitting diodes (LEDs) suffer from color instability under applied bias. Developing narrow-bandwidth deep-blue emitters will maximize the color gamut of display technologies. Mixed anion approaches suffer from halide segregation that leads to their spectral instability. Here instead, a mixed cation strategy is employed whereby Rb+ is directly incorporated during synthesis into CsPbBr3 nanocrystals. Blue-emitting perovskite quantum dots (QDs) with stable photoluminescence, PLQYs greater than 60%, tunable emission from 460 to 500 nm, and narrow emission linewidths (<25 nm) are reported. The strategy retains a pure bromine crystal structure resulting in color-pure stable electroluminescence at operating voltages of up to 10 V, peak external quantum efficiencies (EQEs) of 0.87% and 0.11% for sky-blue (490 nm), and deep-blue (464 nm) devices. The sky-blue devices exhibit the highest combined luminance of 93 cd m?2 at an EQE of 0.75%, the best reported to date of perovskite QD LEDs.
关键词： perovskite quantum dots,LEDs,light-emitting diodes,halide perovskites,blue emission
更新于2025-09-19 17:13:59
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The in vitro Photoinactivation of Helicobacter pylori by a Novel LED-Based Device
摘要： The rise of antibiotic resistance is the main cause for the failure of conventional antibiotic therapy of Helicobacter pylori infection, which is often associated with severe gastric diseases, including gastric cancer. In the last years, alternative non-pharmacological approaches have been considered in the treatment of H. pylori infection. Among these, antimicrobial PhotoDynamic Therapy (aPDT), a light-based treatment able to photoinactivate a wide range of bacteria, viruses, fungal and protozoan parasites, could represent a promising therapeutic strategy. In the case of H. pylori, aPDT can exploit photoactive endogenous porphyrins, such as protoporphyrin IX and coproporphyrin I and III, to induce photokilling, without any other exogenous photosensitizers. With the aim of developing an ingestible LED-based robotic pill for minimally invasive intragastric treatment of H. pylori infection, it is crucial to determine the best illumination parameters to activate the endogenous photosensitizers. In this study the photokilling effect on H. pylori has been evaluated by using a novel LED-based device, designed for testing the appropriate LEDs for the pill and suitable to perform in vitro irradiation experiments. Exposure to visible light induced bacterial photokilling most effectively at 405 nm and 460 nm. Sub-lethal light dose at 405 nm caused morphological changes on bacterial surface indicating the cell wall as one of the main targets of photodamage. For the first time endogenous photosensitizing molecules other than porphyrins, such as flavins, have been suggested to be involved in the 460 nm H. pylori photoinactivation.
关键词： flavins,porphyrins,LEDs,antimicrobial PDT,Helicobacter pylori
更新于2025-09-19 17:13:59
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Enhancement of Emission Intensity in Dy <sup>3+</sup> -Doped ZnO/ZnF <sub/>2</sub> Phosphoborate Glasses for W-LED Materials
摘要： Presently, white light emitting diodes (W-LEDs) were be used to substitute for conventional incandescent and fluorescent lamps due to their advantages; thus, it gets attention to create Dy3+-doped zinc phosphoborate glasses for enhancing better lightness. In this research, the replacing of ZnO by ZnF2 in 49B2O3:30P2O5:(20-x)ZnO:xZnF2:1Dy2O3 glasses, 0 ≤ x ≤ 20 mol% were prepared by melt quenching method and investigated through optical absorption and photoluminescence properties. The absorption results can be used for calculating the Judd-Ofelt (JO) intensity parameters (Ωλ, λ = 2, 4 and 6) and led to predicting the stimulated emission in present glasses. The trend of JO parameters is found to be Ω2 > Ω4 > Ω6 for all glasses. Nevertheless, replacing of ZnF2 does not affect position and intensity of optical absorption of Dy3+-doped glasses, whereas the observed blue (481 nm), yellow (573 nm) and red (662 and 752 nm) emission intensities of photoluminescence spectra rise with ZnF2 contents; the emission intensity at 573 nm for 20ZnF2 show the highest and was higher than 20ZnO around 1.6 times. The emission color of Dy3+-doped zinc phosphoborate glasses has been evaluated with CIE 1931 chromaticity diagram. The results revealed that all glasses emit white light. Hence, these glasses may be suitable candidate for using in W-LED and lighting materials.
关键词： optical absorption,Judd-Ofelt parameters,photoluminescence,ZnF2,W-LEDs,zinc phosphoborate glasses,Dy3+-doped
更新于2025-09-19 17:13:59
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Investigation of Electrical Properties and Reliability of GaN-Based Micro-LEDs
摘要： In this paper, we report high-performance Micro-LEDs on sapphire substrates, with pixel size scaling to 20 μm and an ultra-high current density of 9902 A/cm2. The forward voltages (VF) of the devices ranged from 2.32 V to 2.39 V under an injection current density of 10 A/cm2. The size and structure-dependent effects were subsequently investigated to optimize the device design. The reliability of Micro-LED devices was evaluated under long-aging, high-temperature, and high-humidity conditions. It was found that Micro-LED devices can maintain comparable performance with an emission wavelength of about 445 nm and a full width at half maximum (FWHM) of 22 nm under extreme environments. Following this, specific analysis with four detailed factors of forward voltage, forward current, slope, and leakage current was carried out in order to show the influence of the different environments on different aspects of the devices.
关键词： GaN-based micro-LEDs,micro-LED display,reliability test
更新于2025-09-19 17:13:59