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Photoluminescence Characteristics of Sm3+-doped LnBWO6 (Ln=La, Gd and Y) as New Orange-red Phosphors
摘要： A series of Sm3+-doped LnBWO6 (Ln=La, Gd and Y) phosphors with orange-red light emitting in pure phase were prepared by high temperature solid-state process. The crystal structure, photoluminescence properties, decay lifetimes and thermal stability properties of those as-prepared samples were investigated. Those phosphors can be efficiently excited by near-UV and blue light and emitted orange-red luminescence with color coordinates (0.622, 0.377). Among those LnBWO6 (Ln=La, Gd and Y) hosts, the emission intensities of Sm3+-doped LaBWO6 are the strongest ones. The optimum doping concentration and critical energy transfer distance of Sm3+ ions in LaBWO6 were determined. The fluorescence concentration quenching mechanism was attributed to the dipole-dipole interaction between the Sm3+ ions. The fluorescent thermal quenching studies showed Sm3+ doped LaBWO6 had high thermal-stable properties. The present work suggested that Sm3+-doped LnBWO6 (Ln=La, Gd and Y) as orange-red phosphors exhibited potential application in white LED.
关键词： red phosphors,concentration quenching,energy transfer,white LEDs,luminescent properties
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Internet of Things and Intelligence System (IOTAIS) - BALI, Indonesia (2018.11.1-2018.11.3)] 2018 IEEE International Conference on Internet of Things and Intelligence System (IOTAIS) - Optical Internet of Things within 5G: Applications and Challenges
摘要： The fifth generation (5G) telecommunications standards are being developed to meet the growing demands for high-speed wireless networks (i.e., few tens of Gigabits per second). The 5G standard stems largely from an increasing number of users and plethora of different devices, collectively referred to as smart devices, connecting to a network as part of Internet-of-Things (IoT). A few potential technologies have emerged for 5G such as millimeter waves, massive multiple-input multiple-output, and small cell communications. Although these technologies would satisfy the requirements of 5G, there is a complementary alternative wireless technology of optical wireless communications (OWC), which is being considered. As part of OWC, visible light communications (VLC) and optical camera communications (OCC) are the most attractive options for 5G networks and beyond. VLC with huge frequency spectrum integrated with IoT can open up a wide range of indoor and outdoor applications as part of future smart environments. This paper provides an overview of the all-optical IoT (OIoT) focusing on VLC and OCC based potential applications and challenges as part of 5G standards.
关键词： light emitting diodes (LEDs),visible light communications (VLC),Internet of things (IoT),Optical wireless communications (OWC),optical camera communications (OCC)
更新于2025-09-23 15:22:29
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Achieving Near-Unity Photoluminescence Efficiency for Blue-violet Emitting Perovskite Nanocrystals
摘要： While the perovskite nanocrystals (NCs) have shown great promise as materials for efficient light emitting diodes (LEDs), low photoluminescence quantum yield (PLQY) of the blue-emitting perovskites is an impediment to the development of white LEDs of which blue is an essential component. Herein, we report that room temperature post-synthetic treatment of weakly blue-violet emitting (PLQY 3%) CsPbCl3 NCs with CdCl2 results in an instantaneous enhancement of the PLQY to near-unity without affecting the PL peak position (406 nm) and spectral width. The time-resolved PL and ultrafast transient absorption measurements confirm the removal of nonradiative defect states of the CsPbCl3 NCs in treated sample. The elemental composition and structural data of the treated sample reveal facile doping of Cd2+ into the crystal lattice without affecting the size and shape of the NCs. Extraordinary PLQY, high air- and photo-stability and ease of preparation of this Cd-doped CsPbCl3 make it by far the most attractive blue-emitting perovskite for development of efficient blue and white LEDs.
关键词： photoluminescence quantum yield,blue-emitting perovskites,perovskite nanocrystals,CdCl2 treatment,white LEDs
更新于2025-09-23 15:21:21
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Tuning phosphors for better white light
摘要： Light-emitting diodes (LEDs) that produce white light are about to take over the lighting world. The U.S. market share of these super-long-lasting, cool-to-the-touch lights, which use less than a quarter of the energy of conventional incandescent bulbs, sits around 10%. Industry watchers predict that number will exceed 80% by 2030, reducing power consumption in the U.S. by 40%. Chemists are taking a leading role in this technology, which underpins general lighting and electronic displays, by customizing the emission spectrum, stability, and other properties of inorganic phosphors in the LEDs that help produce finely tuned white light.
关键词： energy efficiency,inorganic phosphors,color rendering index,LEDs,white light
更新于2025-09-23 15:21:21
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3-Hydroxyflavone and N-phenylglycine in High Performance Photoinitiating Systems for 3D Printing and Photocomposites Synthesis
摘要： In this work, we propose to use 3-hydroxyflavone as a versatile high performance visible light photoinitiator (PIs) in combination with an amino acid (N-phenylglycine) for the free radical polymerization (FRP) of methacrylates in thick samples or composites upon visible light exposure (Light-Emitting Diode LED@405 nm or LED@477 nm). The high originality of this approach is the use of safer compounds in photoinitiating systems (flavone derivative/amino acid). 3-Hydroxyflavone can also be used in three-component systems with an iodonium salt and an amine for the cationic polymerization of epoxides upon exposure to near UV light LED@385 nm. Also interestingly, a charge transfer complex CTC between N-phenylglycine NPG and iodonium salt gives also remarkable initiating performance for free radical polymerization of methacrylates upon mild light irradiation conditions (LED@405 nm). High polymerization initiating abilities are found and high final reactive function conversions are obtained. The use of the new proposed initiating systems as materials for laser write or 3D printing experiments was also especially carried out with the formation of printed green fluorescent photopolymers. This green fluorescence obtained with naturally occurring 3-hydroxyflavone compound can be ascribed to the excited state intramolecular proton transfer ESIPT character. A full picture of the included photochemical mechanisms is given. Remarkably, 3-hydroxyflavone is also very efficient for photocomposites synthesis with glass fibers (thick samples with good depth of cure) using UV or LED@395 nm conveyor.
关键词： 3D printing,Cationic polymerization,Light-Emitting Diodes (LEDs),Free radical polymerization,photoinitiators,composites
更新于2025-09-23 15:21:21
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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Future Photometry Based on Solid-State Lighting Products - Joint Research Project of European Metrology Institutes
摘要： Luminous flux (lm) and active electrical power consumption (W) of new SSL products coming to market are measured at test laboratories in order to determine the luminous efficacy (lm/W) and energy class of the products. Due to the fact that spectral responsivities of V(λ)-filtered photometers differ from the defined CIE V(λ) curve, all photometers are typically calibrated using light with correlated colour temperature (CCT) of 2856 K. This causes unwanted spectral errors in the measurements of SSL products at test laboratories and also in the field due to the large differences in the spectra of calibration sources and the light being measured, and in many cases cannot be corrected for. The EMPIR (European Metrology Programme for Innovation and Research) project 15SIB07 PhotoLED addresses the obsolescence of traditional incandescent standard lamp technology used in photometry and the need to support the introduction and uptake of solid-state lighting (SSL) products. It develops and validates the basis for a new photometric system based on white LEDs, by developing new LED-based calibration sources and measurement techniques supporting the specific properties of the new light sources and detector technology including illuminance measurement of the new LED-sources without optical V(λ)-filters in the calibration of photometers and measurement facilities used for determining the energy efficiency of new SSL products coming to market.
关键词： SSL products,new light source,LEDs
更新于2025-09-23 15:21:21
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Suggestions on Efficiency Droop of GaN-based LEDs
摘要： InGaN/GaN-based light-emitting diodes (LEDs) are widely used in modern society and industry among different areas. However, InGaN/GaN LEDs suffer from an efficiency droop issue: The internal efficiency decreases during high current injection. The efficiency droop significantly affects the development of GaN-based LEDs devices in efficiency and light-output areas. Therefore, the improvement of the droop phenomenon has become a significant topic. This paper introduces several possible mechanisms of droop phenomenon based on different hypotheses including Auger Recombination, Carrier Delocalization and Electron Leakage. Furthermore, some proposals to mitigate efficiency droop, including semipolar LEDs, electron blocking layer(EBL), quaternary alloy and chip design will be discussed and analyzed. Also, it will provide some suggestions for the further optimization of droop phenomenon in each proposal.
关键词： electron blocking layer,semipolar LEDs,GaN-based LEDs,Auger Recombination,chip design,quaternary alloy,Carrier Delocalization,Electron Leakage,efficiency droop
更新于2025-09-23 15:21:01
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Bright Blue Light Emission of Ni2+ ions doped CsPbClxBr3-x Perovskite Quantum Dots Enabling Efficient Light-Emitting Devices
摘要： In recent years, significant advances have been achieved in the red and green perovskite quantum dots（PQDs）based light-emitting diodes (LEDs). However, the performances of the blue perovskite LEDs are still seriously lagging behind that of the green and red counterparts. Herein, we successfully developed Ni2+ ions doped CsPbClxBr3-x PQDs through the room-temperature supersaturated recrystallization synthetic approach. We simultaneously realized the doping of various concentrations of Ni2+ cations, and modulated the Cl/Br element ratios through introducing different amount of NiCl2 solution in the reaction medium. By the synthetic method, not only the emission wavelength from 508 to 432 nm of Ni2+ ions doped CsPbClxBr3-x QDs was facially adjusted, but also the photoluminescence quantum yield (PLQY) of PQDs was greatly improved due to efficiently removing the defects of the PQDs. Thus, the blue emission at 470 nm with PLQY of 89% was achieved in 2.5% Ni2+ ions doped CsPbCl0.99Br2.01 QDs, which increased nearly three times over that of undoped CsPbClBr2 QDs, and was the highest for the CsPbX3 PQDs with blue emission that fulfilling the NTSC standards. Benefiting from the high luminous Ni2+ ions doped PQDs, the blue emitting LED at 470 nm was obtained, exhibiting an external quantum efficiency (EQE) of 2.4% and a maximum luminance of 612 cd/m2, which surpassed the best performance reported previously for the corresponding blue-emitting PQDs based LED.
关键词： perovskite QD-LEDs,Ni2+ ion doping,blue emission,anion exchange,perovskite quantum dots
更新于2025-09-23 15:21:01
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Enhance the efficiency of green-yellow LED by optimizing the growth condition of preparation layer
摘要： The effects of the preparation layer grown under different conditions, which is an InGaN/GaN SLs structure inserted between the n-GaN layer and the MQWs, on the performance of green-yellow LED have been investigated. In this paper, the quality of InGaN/GaN multiple quantum wells (MQWs) and the optoelectronic properties of LED have been focused on. According to the experimental results, when the growth temperature of GaN barriers in SLs was increased, the interface between InGaN layers and GaN layers became more abrupt, and the indium distribution in the quantum wells became more uniform. In consequence, the forward voltage was reduced, the external quantum efficiency (EQE) was improved. By decreasing the growth rate of the high temperature barriers, the indium uniformity became even better, forward voltage was reduced again and EQE was further improved.
关键词： Preparation layer,Si substrates,Localized site,Crystal quality,Green-yellow LEDs
更新于2025-09-23 15:21:01
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Full-visible-spectrum lighting enabled by an excellent cyan-emitting garnet phosphor
摘要： The development of phosphor materials with outstanding photoluminescence properties is critical for next-generation high-quality solid-state white lighting. As there is a blue-green cavity existed in the emission spectra of the traditional phosphor-converted white-light-emitting diodes (w-LEDs), cyan-emitting phosphor serves an important function in compensating the spectral gap to realize the “full-visible-spectrum lighting”. Herein, we reported the discovery of an efficient cyan-emitting Ce3+-doped Ca2YHf2Al3O12 (CYHAO) garnet phosphor with good thermal stability. The as-prepared CYHAO:Ce3+ phosphor exhibited a broad excitation band in the range of 360 to 460 nm with a maximum at 408 nm, making this phosphor compatible with an efficient 400 nm NUV-emitting LED chip. Under the 408 nm excitation, the optimal sample of CYHAO:0.03Ce3+ exhibited bright broadband cyan emission (λem = 493 nm; bandwidth = 100 nm) together with extra-high internal quantum efficiency (IQE) of 89.5% and external quantum efficiency (EQE) of 69.1%. Notably, the as-prepared CYHAO:0.03Ce3+ phosphor showed good thermal stability (64.2% of emission intensity retained at 423K) and excellent color stability when working in the temperature range of 303-463 K. Importantly, the constructed w-LED device exhibited bright well-distributed warm white light with high color rendering index (CRI; Ra = 93.5 and R12 = 90.4) and low correlated color temperature (3700 K) under 60 mA driven current, indicating that the title cyan phosphor can be utilized as the compensation of the blue-green cavity to apply in full-visible-spectrum lighting. Furthermore, these findings provide new insights into exploring high-performance cyan phosphors for NUV-pumped high-CRI warm w-LEDs.
关键词： White LEDs,Color rendering index,Cyan emissions,Phosphors,Full-visible-spectrum lighting
更新于2025-09-23 15:21:01