- 标题
- 摘要
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- 实验方案
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Ultraviolet LED Technology for Food Applications || Technology of LED Light Sources and Systems From Visible to UV Range
摘要： The basic of light-emitting diodes (LEDs) technology and manufacturing features will be presented in this chapter. The fundamental principles of light emission by semiconducting materials, design of LEDs chips and types of packages, requirements to LEDs system are discussed for better understanding of this new light technology. The differences and application areas in production and postharvest processing of fruit and vegetables of visible and UV LEDs are also included to better understand LEDs potential in food industry.
关键词： LED chip,LED package and LED system,Visible and UV LEDs
更新于2025-09-16 10:30:52
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Stability and degradation of AlGaN-based UV-B LEDs: Role of doping and semiconductor defects
摘要： Within this paper, we present an extensive analysis of the degradation of UV-B light-emitting diodes (LEDs) submitted to constant current stress. The study is based on combined electrical, optical and spectral characterization, and capacitance deep-level transient spectroscopy (C-DLTS). The results of this analysis demonstrate that the decrease in the optical power during the stress is stronger at low measuring current levels, indicating that the degradation is related to the increase in Shockley-Read-Hall (SRH) recombination. The electrical characterization shows a decrease in the driving voltage, probably due to an increased activation of the Mg dopant, and an increase in the sub-threshold forward current, that suggest a generation of mid-gap states during the stress. C-DLTS measurements were carried out to study the variation in defects concentration after stress; the most relevant traps were ascribed to the presence of Mg doping and/or to intrinsic defects related to the GaN growth.
关键词： doping,semiconductor defects,degradation,DLTS,UV-B LEDs
更新于2025-09-16 10:30:52
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Perovskite quantum dots for light-emitting devices
摘要： Perovskite quantum dots (QDs) have been hotly pursued in recent decades owing to their quantum confinement effect and defect-tolerant nature. Their unique optical properties, such as high photoluminescence quantum yield (PLQY) approaching unity, narrow emission bandwidth, tunable wavelength spanning the entire visible spectrum, and compatibility with flexible/stretchable electronics, render perovskite QDs promising for next-generation solid lighting sources and information displays. Herein, the advances in perovskite QDs and their applications in LEDs are reviewed. Strategies to fabricate efficient perovskite QDs and device configuration, including material composition design, synthetic methods, surface engineering, and device optimization, are investigated and highlighted. Moreover, the main challenges in perovskite QDs of instability and toxicity (lead-based) are identified, while the solutions undertaken with respect to composition engineering, device encapsulation, and lead-replacement QDs are demonstrated. Meanwhile, perspectives for the further development of perovskite QDs and corresponding LEDs are presented.
关键词： device encapsulation,quantum confinement,Perovskite quantum dots,LEDs,instability,composition engineering,flexible electronics,photoluminescence,lead-replacement,stretchable electronics,toxicity,light-emitting devices
更新于2025-09-16 10:30:52
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[IEEE 2019 International Conference on Advances in Big Data, Computing and Data Communication Systems (icABCD) - Winterton, South Africa (2019.8.5-2019.8.6)] 2019 International Conference on Advances in Big Data, Computing and Data Communication Systems (icABCD) - A Sensor for Monitoring the Lifespan of Color-LEDs in Traffic Lights
摘要： This paper has explored an effective monitoring of Red, Green and Yellow colors using visible-light communication systems (VLC) as a backbone on traffic lights for easy detection of traffic control light colors in South Africa as well as African continent in context to the problem of consistency in the ON state of traffic control frequency information of detected colors is employed to determine their state for prompt response to the road users. The lifespan of each light emitting diode (LED) dies gradually due to constant heat in the ON-state thus leave some traffic lights not attended. This negligence is because of weak network monitoring techniques which result in vehicle-to-vehicle accidents (V2V), vehicle-to-pedestrian accidents (V2P) and vehicle-to-motorcycle (V2M) accidents. The researchers deploy a TCS3200 pixel color sensor to monitor the lifespan of each LED color in the traffic light and using their variation in frequency to yield the LEDs lifespan, linking them with one central network for display. This experiment guarantees the road users of a steady traffic light to regulate the passing of vehicles without any accident both in frost, high winds and raining season.
关键词： RGB LEDs,Visible light communication (VLC),intensity,CIE 1931
更新于2025-09-16 10:30:52
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Thermal Impact of LED Chips on Quantum Dots in Remote-Chip and On-Chip Packaging Structures
摘要： Light-emitting diode (LED) chips in quantum dot (QD)-converted LEDs serve simultaneously as a heat source and a heat sink, but it remains unclear which of these is the major factor that affects the operating temperature of QDs. Here, we investigated the thermal and optical performances of QD-converted LEDs using QD-on-chip and QD-remote-chip packaging structures, to better understand the thermal effect of LED chips on QDs. Our results indicated that the QD-on-chip structure achieved the same optical performance as the QD-remote-chip structure, while the former can save QD usage up to 75.9% owing to the higher absorption probability of QDs closer to the blue source. Most importantly, the QD-on-chip structure largely reduced the maximal surface temperature from 82.7 ?C to 60.2 ?C at 250 mA, and had a longer operating lifetime compared with the QD-remote-chip structure. Simulations revealed that the QD-remote-chip structure could suppress the heat transfer from chips to QDs; however, the hot spot remained in QDs, owing to the heavy conversion loss and low thermal conductivity of the silicone matrix; consequently, the QD-on-chip structure had better heat dissipation (lower temperature) for QDs closer to the chip that served as heat sinks. Therefore, it is suggested to place QDs near the heat sink with high thermal conductivity, such as the LED chip, for heat dissipation; this is better than removing QDs for blocking the heat generated by the LED chip.
关键词： Light-emitting diodes (LEDs),quantum dot (QD),packaging structure,thermal and optical performance
更新于2025-09-16 10:30:52
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Comparison of Currenta??Voltage Response to Diagnostic X-rays of Five Light-Emitting Diode Strips
摘要： Light-emitting diodes (LEDs) have miscellaneous applications owing to their low cost, small size, flexibility, and commercial availability. Furthermore, LEDs have dual applicability as light emitters and detectors. This study explores the current–voltage (C–V) response of LED strips exposed to diagnostic x-rays. Cold white, warm white, red, green, and blue LED strip colors were tested. Each strip consisted of 12 LED chips and was connected to a multimeter. The variable diagnostic x-ray parameters evaluated were kilovoltage peak (kVp), milliampere-seconds (mAs), and source-to-image distance (SID). The radiation dose was also measured using a dosimeter simultaneously exposed to x-rays perpendicularly incident on the strips. Lastly, the consistency of C–V responses, and any possible degradation after 1–2 months was also analyzed. Each LED strip color was ranked according to its C–V response in each of the investigated parameters. The LED strip color with the best cumulative rank across all the tested parameters was then examined for reproducibility. Our findings revealed that the C–V responses of LED strips are (a) generally low but measurable, (b) inconsistent and fluctuating as a consequence of kVp variations, (c) positively correlated to mAs, (d) negatively correlated to SID, and (e) positively correlated to dose. Overall results suggested cold white LED strip as most feasible for x-ray detection—in comparison to examined colors. Additionally, the reproducibility study using the cold white LED strip found a similar trend of C–V response to all variables except kVp. Outcomes indicate that LED strips have the potential to be exploited for detecting low dose (~0–100 mGy) diagnostic x-rays. However, future studies should be carried out to increase the low C–V signal.
关键词： LED strip,photonic device,radiation-induced signal,application of LEDs,C–V Response,diagnostic x-rays
更新于2025-09-16 10:30:52
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Demonstration of low forward voltage InGaN-based red LEDs
摘要： Here we report InGaN-based red light-emitting diodes (LEDs) grown on (201) β-Ga2O3 substrates. AlN/AlGaN strain-compensating layers and hybrid multiple-quantum-well structures were employed to improve the crystalline-quality of the InGaN active region. A bare LED showed that peak wavelength, light output power, and external quantum efficiency were 665 nm, 0.07 mW, and 0.19% at 20 mA, respectively. As its forward voltage was 2.45 V at 20 mA, the wall-plug efficiency was 0.14%. The characteristic temperature of the LEDs was 222 K at 100 mA evaluated from the temperature dependence of electroluminescence.
关键词： InGaN,β-Ga2O3 substrates,red LEDs,multiple-quantum-well structures,strain-compensating layers
更新于2025-09-16 10:30:52
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Amplification of Radiation-Induced Signal of LED Strip by Increasing Number of LED Chips and Using Amplifier Board
摘要： Transducers, such as photodiodes, phototransistors, and photovoltaic cells are promising radiation detectors. However, for accurate radiation detection and dosimetry, signals that emanate from these devices have to be sufficient to facilitate accurate calibrations, i.e., assigning a quantity of radiation dose to a specific magnitude of the signal. More so, purposely fabricated for luminescence, LEDs produce significantly low signals during radiation detection applications. Therefore, this paper investigates the enhancement and augmentation of photovoltaic signals that were generated when LED strips were being exposed to diagnostic X-rays. Initially, signal amplification was achieved through increasing the effective LED active area (from 60 to 120 chips); by successively connecting LED strips. Further, signal amplification was undertaken by injecting the raw LED strip signal into an amplifier board with adjustable gains. In both the signal amplification techniques, the tube voltage (kVp), tube current-time product (mAs), and source-to-detector distance (SDD) were varied. The principal findings show that effective active area-based signal amplifications produced an overall average of 91.16% signal enhancement throughout all of the X-ray parameter variations. On the other hand, the amplifier board produced an average of 36.48% signal enhancement for the signals that were injected into it. Chip number increment-based signal amplifications had a 0.687% less coefficient of variation than amplifier board signal amplifications. The amplifier board signal amplifications were impaired by factors, such as dark currents, amplifier board maximum operational output voltage, and saturation. Therefore, future electronic signal amplification could use amplifier boards having low dark currents and high operational voltage headroom. The low-cost and simplicity that are associated with active-area amplification could be further exploited in a hybrid amplification technique with electronic amplification and scintillators.
关键词： tube current-time product (mAs),application of LEDs,amplifier board,LED active area,source-to-detector distance (SDD),diagnostic X-rays,tube voltage (kVp)
更新于2025-09-16 10:30:52
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Enhanced emission from thermally stable Eu3+ doped CaB2Si2O8 red phosphors via alkali metal modification for W-LEDs application
摘要： M+/Eu3+ (M = Li, Na, K) co-doped CaB2Si2O8 phosphors have been synthesized by a solid-state reaction approach. XRD measurements confirm that the phase purity of the CaB2Si2O8 host is maintained after the introduction of alkali metal ions and Eu3+ ions. The emission intensity of Eu3+ ions is enhanced by a factor of 1.75 and 1.55 with the incorporation of Li+ and Na+ ions, respectively, originating from the charge compensation and improved asymmetry in the crystal field, while the addition of K+ ions to the composition results in a decreased luminescence intensity due to the structural-defect-related quenching. Temperature dependent measurement reveals that the prepared phosphor exhibits excellent thermal stability with 81% at 423 K of the integrated emission intensity at 298 K. A white light-emitting diode (W-LED) device is fabricated based on the synthesized Eu3+ doped CaB2Si2O8 red phosphor modified by Li ions. All these results indicate that the synthesized phosphor is a promising red-emitting material for W-LEDs application.
关键词： Red phosphor,Eu3+ ions,W-LEDs,Alkali metal ions
更新于2025-09-16 10:30:52
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Efficient and Stable Inverted Quantum Dot Light-Emitting Diodes Enabled by An Inorganic Copper-Doped Tungsten Phosphate Hole-Injection Layer
摘要： Inorganic interfacial buffer layers have widely been employed for efficient and long lifetime optoelectronic devices due to their high carrier mobility and excellent chemical/thermal stability. In this paper, we developed a solution-processed inorganic tungsten phosphate (TPA) as hole injection layer (HIL) in inverted quantum dot light-emitting diodes (QLEDs) achieving a high external quantum efficiency (EQE) of up to ~20%. Further, the copper ions are doped into tungsten phosphate (Cu:TPA) which leads to an enhancement in hole injection due to increased hole mobility and conductivity of TPA as well as decreased hole injection barrier, enabling better charge balance in QLEDs and lower turn-on voltage from 5 to 2.5 V. Compared with the devices using conventional organic poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) HIL, the half-lifetime of Cu:TPA-based devices is over 3000 h at an initial brightness of 100 cd m-2, almost five-fold operating lifetime enhancement.
关键词： Quantum Dot LEDs,Hole Injection Layer,Copper Doping,Tungsten Phosphate,Electroluminescence
更新于2025-09-16 10:30:52