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One-Step Synthesis of White-Light-Emitting Carbon Dots for White LEDs with a High color rendering index of 97

ADVANCED SCIENCE 2023年第12期10卷 e2206386页

作者： Yan, Zishan Chen, Tong Yan, Lingpeng Liu, Xinghua Zheng, Jingxia Ren, Fu-de Yang, Yongzhen Liu, Bin Liu, Xuguang Xu, Bingshe Taiyuan Univ Technol Key Lab Interface Sci & Engn Adv Mat Minist Educ Taiyuan 030024 Peoples R China Shanxi Zheda Inst Adv Mat & Chem Engn Taiyuan 030032 Shanxi Peoples R China Taiyuan Univ Technol Coll Mat Sci & Engn Taiyuan 030024 Peoples R China North Univ China Sch Energy & Power Engn Taiyuan 030051 Peoples R China North Univ China Sch Chem Engn & Technol Taiyuan 030051 Peoples R China

White-light-emitting carbon dots (WCDs) show innate advantages as phosphors in white light-emitting diodes (WLEDs). For WLEDs, the color rendering index (CRI) is the most important metric to evaluate its performance. Herein, WCDs are prepared by a facile one-step solvothermal reaction of trimellitic acid and o-phenylenediamine. It consists of four CDs identified by column chromatography as blue, green, yellow, red, and thus white light is a superposition of these four types of light. The mixture of the four CDs undergoes Forster resonance energy transfer to induce the generation of white light. The photoluminescence of WCDs originates from the synergistic effect of carbon core and surface states. Thereinto, the carbon core states dominate in RCDs, and the increase of amide contents and degree of conjugation promote the redshift of the emission spectra, which is further confirmed by theoretical calculations. In addition, a high CRI of 97 is achieved when the WCDs are used as phosphors to fabricate WLEDs, which is almost the highest value up to now. The multicolor LEDs can also be fabricated by using the four multicolor CDs as phosphors, respectively. This work provides a novel approach to explore the rapid preparation of low-cost, high-performance WCDs and CDs-based WLEDs.

关键词： color rendering index multicolor white light-emitting diodes white-light-emitting carbon dots

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Enhancement of color rendering index of stable lead-free perovskite WLEDs through incorporating green carbon dots

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CERAMICS INTERNATIONAL 2023年第17期49卷 28741-28750页

作者： Sun, Wenfeng Li, Xue Li, Bo Wang, Caizheng Zhao, Ying Zu, Xiaotao Zhou, Weilie Xiang, Xia Univ Elect Sci & Technol China Sch Phys Chengdu 610054 Peoples R China Univ Elect Sci & Technol China Shenzhen Inst Adv Study Shenzhen 518110 Peoples R China Univ New Orleans Dept Phys New Orleans LA 70148 USA Univ New Orleans Adv Mat Res Inst New Orleans LA 70148 USA

In this work, the carbon quantum dots@Cs2NaInCl6 (CDs@CNC) composites are presented by a facile solution synthesis. The obtained CDs@CNC composites maintain the octahedral morphology of original CNC host and the characteristic functional groups of original CDs. As a result, the rare-earth-free CDs@CNC composites exhibit green light emission with good stability for UV irradiation, heat, and humidity. In addition, CDs were combined with ion-doped CNC to obtain multicolor phosphor and the corresponding white light emitting diode (WLED) devices were fabricated by coating composites on commercial UV chips. The color render index (CRI) of WLEDs increases significantly from 66.24 to 90.95 while the cold-warm white fluorescence can be flexibly tuned by the change of excitation wavelength. The combination of CDs and double perovskites provide a new route to design white light emission phosphors, which could lead to the fabrication of next generation high-quality lighting devices.

关键词： Carbon dots Cs2NaInCl6 Rare-earth-free color rendering index White light-emitting diodes

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Tunable Bright White Light Emission with Ultra-High color rendering index Induced by Trigonal Bipyramid Unit

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ADVANCED OPTICAL MATERIALS 2023年第3期11卷

作者： Lin, Jiawei Guo, Zhongnan Liu, Kunjie Sun, Niu Cao, Jindong Chen, Xin Zhao, Jing Liu, Quanlin Yuan, Wenxia Univ Sci & Technol Beijing Sch Chem & Biol Engn Dept Chem Beijing 100083 Peoples R China Univ Sci & Technol Beijing Sch Mat Sci & Engn Beijing Municipal Key Lab New Energy Mat & Technol Beijing 100083 Peoples R China Univ Sci & Technol Beijing Inst Solid State Chem Beijing Adv Innovat Ctr Mat Genome Engn Beijing 100083 Peoples R China

Efficient broadband emitting organic-inorganic metal hybrids (OIMHs) have attracted great attention recently as promising single-component white light emitters. Here a new zero-dimensional (0D) OIMH (C13H14N)(2)InCl5 (C13H14N+ = N-methyldiphenylammonium) is reported, which features unique five-coordinated [InCl5](2-) trigonal bipyramid motif. For the first time, it is demonstrated that the trigonal bipyramid units in 0D OIMH can act as luminescence centers, showing blue emission under UV light. Remarkably, incorporating Sb3+ in [InCl5](2-) trigonal bipyramids induces a new dual-band emission at 540 and 735 nm resulting from the singlet and triplet self-trapped excitons in [SbCl5](2-), leading to complete coverage of the entire visible spectrum. The resulting emissions in (C13H14N)(2)InCl5:Sb3+ are tunable from cold to warm white with the correlated color temperatures changing from 5574 to 3473 K and more importantly, an ultra-high color rendering index (CRI) up to 96 being observed, which is comparable to the highest value in hybrid metal halides. A high photoluminescence quantum yield of 46.26% is simultaneously obtained in this system. This work demonstrates that the 0D OIMH with trigonal bipyramid motif is an excellent system for realizing the single-component white light emission with both high efficiency and ultra-high CRI.

关键词： color rendering index multi-band photoluminescence trigonal bipyramid white light zero-dimensional metal halides

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Full-spectrum solid-state white lighting with high color rendering index exceeding 96 based on a bright broadband green-emitting phosphor

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APPLIED MATERIALS TODAY 2022年 27卷

作者： Chan, Jingming Devakumar, Balaji Li, Wei Ma, Nan Huang, Xiaoyong Lee, Adam F. Taiyuan Univ Technol Coll Phys & Optoelect Taiyuan 030024 Peoples R China Sri Vidya Mandir Arts & Sci Coll Dept Phys Krishnagiri 636902 Tamil Nadu India RMIT Univ Ctr Adv Mat & Ind Chem CAMIC Melbourne Vic 3000 Australia

Developing blue-light-excited high-efficiency phosphor remains challenging for the fabrication of warm white light-emitting diodes (LEDs) with an ultra-high color rending index (CRI). Here, the co-substitution of Ca2 +-Hf4+ ion-pairs into a Y3Al5O12:Ce3+ phosphor, affords a novel, broadband, green-emitting CaY2HfAl4O12:2%Ce3+ garnet-type phosphor amenable to efficient blue light excitation. The structure, luminescent properties and blue-shift of this new material relative to a Y3Al5O12:2%Ce3+ phosphor have been extensively studied. Under 450 nm excitation, the optimum material exhibits high internal quantum efficiency (73.3%) and excellent thermal stability. Incorporation of the CaY2HfAl4O12:2%Ce3+ green phosphor into a prototype LED device delivers full-spectrum lighting with a high CRI (Ra = 97.2, R9 = 98.3) and low correlated color temperature (CCT = 3508 K). The resulting insight should aid the development of novel high-efficiency phosphors for full-spectrum warm-white LEDs with high-CRI value.(c) 2022 Elsevier Ltd. All rights reserved.

关键词： Co-substitution Garnet compounds Full-spectrum lighting color rendering index Quantum efficiency

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Optimising Absorption in Luminescent Solar Concentrators constraint by Average Visible Transmission and color rendering index

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FRONTIERS IN PHYSICS 2022年 10卷

作者： de Bruin, Thomas A. van Sark, Wilfried G. J. H. M. Univ Utrecht Copernicus Inst Sustainable Dev Utrecht Netherlands

The luminescent solar concentrator (LSC) as energy harvesting window is an emerging technology in the realm of building integrated photovoltaics. Using recent advancement for assessing the balance between transmitted color quality and potential electricity generation, this paper optimizes theoretical luminophore absorption spectra for the highest power generation possible. The power conversion efficiencies (PCE) are based on coupling of the LSC waveguide to a highly efficient crystalline silicon solar cell. A non-convex optimisation algorithm maximizing absorption is used with constraints for color quality parameters: average visible transmission (AVT) and color rendering index (CRI). An optimal luminophore has been defined using a continuous absorption function with a cut-off and limited absorption in the visible spectrum. Two types of constraints are set: 1) 55% < AVT < 100% and 2) 55% < AVT < 100% and 70 < CRI < 100. The first constraint will ensure sufficient visible light and the second ensures appropriate color rendering. Ray-trace validated results show high power conversion efficiencies ranging from 9.53% to 14.3% for (AVT = 90%, CRI = 98) and (AVT = 55%), respectively. Future studies can use these results to benchmark (tandem) LSCs for specific lighting requirements. Furthermore, the flexibility of the proposed method allows for the adaptation to constraints not used in this paper.

关键词： average visible transmission color rendering index luminescent solar concentrator luminophore optimisation

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Neuro-controller for broadcast lighting light-emitting diode to express white light with high color rendering index

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JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY 2022年第2期30卷 115-127页

作者： Park, Sung-Chan Hwang, Kwang-Bok Park, Jin-Hyun Gyeongsang Natl Univ Dept Mechatron Engn Jinju South Korea

Technical characteristics analysis related to correlated color temperature (CCT), color rendering, and illuminance is required to use light-emitting diode (LED) as broadcast lighting. In general, to realize a white light source with a high color rendering index (CRI), we selected the appropriate emission intensity of RGBW LED through trial and error. However, the characteristics of the LED light source and environmental conditions make it difficult to perform the procedure several times. The objective of this study was to design a system that could control illuminance, CCT, and increment uv while having high CRI, as an LED control method for broadcasting lighting. The controller implements using a feed-forward neural network with excellent nonlinear function approximation capability. We measure data directly from the red green blue white (RGBW) LED system for neural network training. We then select data with high CRI from the measured raw data and choose data for neural network learning by removing measurement noise using the quadratic polynomial interpolation method. The performance evaluation confirms that the proposed neural network controller shows excellent results as an RGBW LED controller for broadcast lighting in the Planckian locus and all regions of white light.

关键词： color rendering index correlated color temperature feed-forward neural network RGBW LED system

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Anchoring of red perovskite nanocrystals on YAG:Ce phosphor for high color rendering index WLEDs

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JOURNAL OF ALLOYS AND COMPOUNDS 2022年第0期899卷 163347-163347页

作者： Tang, Yun He, Xiaoqiang Zhang, Yuchao Yuan, Hudie Xin, Yalou Ren, Xiaohu Chen, Qiang Yin, Hongfeng Xian Univ Architecture & Technol Sch Mat Sci & Engn Xian 710055 Shaanxi Peoples R China Northwestern Polytech Univ Sch Mat Sci & Engn State Key Lab Solidificat Proc Xian 710072 Shaanxi Peoples R China

Widespread application of YAG:Ce-based white light-emitting diodes (WLEDs) is being challenged for their poor color rendering index (CRI) and high correlated color temperature (CCT) due to the lack of red emission. Organic-inorganic hybrid perovskite nanocrystals (MAPbX(3) PNCs, X = Cl, Br, I or mixture of them), presenting high photoluminescence quantum yield, tunable emission color and simple fabrication process have been recognized as promising red-emitting component for warm WLEDs. However, additional protection process for PNCs always needed due to their poor stability, which complicates the fabrication procedures of WLEDs. Besides, nano-sized PNCs and micron YAG:Ce powder display different sinking behavior in silicone, which also hard to ensure the uniform distribution of the two components and subsequently stable optical characteristics of the device. Herein, a one-pot anchoring strategy is implemented to realize the enhanced thermal and photo-stabilities of in-situ generated red-emitting MAPbBr(0.5)I(2.5) PNCs and simultaneously strong interaction between the PNCs and YAG:Ce to form PNCs@A-YAG composite, which greatly simplifies the processes, and also avoids the uneven distribution of phosphor and PNCs in silicone. Furthermore, the WLED, fabricated by PNCs@A-YAG and a commercial blue chip, exhibits high CRI of 92, low CCT of 4755 K, and super high saturated red color R9 of 95, which are of vital importance in achieving warm white light for indoor lighting applications. This work could promote the practical application of perovskite nanocrystals in the field of high color rendering index WLEDs. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Perovskite nanocrystals White light-emitting diodes Anchoring Stability color rendering index

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One-Pot Synthesis of Orange Emissive Carbon Quantum Dots for All-Type High color rendering index White Light-Emitting Diodes

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ACS SUSTAINABLE CHEMISTRY & ENGINEERING 2022年第26期10卷 8289-8296页

作者： Guo, Huazhang Liu, Zhikang Shen, Xiaoyu Wang, Liang Shanghai Univ Sch Environm & Chem Engn Inst Nanochem & Nanobiol Shanghai 200444 Peoples R China

The challenges of toxicity and stability of traditional long-wavelength emitting luminescent materials undoubtedly restrain their widespread applications. Some remedial proposals do not fundamentally solve these problems. So, the development of new types of long-wavelength emitting luminescent materials has become a new trend. Herein, orange emissive carbon quantum dots (O-CQDs) are successfully prepared by a simple one-step solvothermal approach using 1-amino-2-naphthol hydrochloride and citric acid (CA). Interestingly, O-CQDs can always be achieved by the regulation of different reaction conditions (e.g., CA concentration, temperature, and reaction times), which is closely related to the fixed structure of O-CQDs inherited from the used precursor. An O-CQD displays its homogeneous size distribution with an average size of 2.5 nm and obtains a high-graphitoid sp(2) hybrid architecture. Impressively, O-CQDs exhibit remarkable photoluminescent (PL) properties, including excitation-independent behavior, thermostability, photostability, and the robust non-solvatochromic effect, in different solvents due to their efficient pi-conjugated system. These excellent properties lay the optical foundation of O-CQDs for the construction of high-performance white-light-emitting diode (WLED) devices. More importantly, O-CQDs are employed as a light regulator combined with yellow emissive CQDs to form the phosphor, and then CQD phosphor-based all-type WLEDs with a high color rendering index (CRI, >= 81) are realized. This work provides a new avenue for the exploration of low-cost, environment-friendly, and high-performance CQD phosphor-based all-type WLEDs using long-wavelength emitting CQDs as a light regulator.

关键词： carbon quantum dots orange molecular fusion method color rendering index WLEDs

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High Stability Carbon Dots Phosphor and Ultra-High color rendering index White Light-Emitting Diodes

IEEE PHOTONICS JOURNAL

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IEEE PHOTONICS JOURNAL 2022年第1期14卷 1页

作者： Yan, Yuxian Yin, Luqiao Guo, Huazhang Wang, Liang Zhang, Jianhua Sch Mat Sci & Engn Shanghai 200444 Peoples R China Key Lab Adv Display & Syst Applicat Shanghai 200072 Peoples R China Sch Environm & Chem Engn Shanghai 200444 Peoples R China

A new kind of carbon dots based phosphor is developed for light emitting diodes (LED) by adsorbing carbon dots to starch particles. The bonding mechanism is based on hydrogen bonding of surface functional groups of carbon dots and starch particles. Aggregation-induced quenching is avoided and the thermal stability of the carbon dots phosphor is enhanced. The carbon dots phosphor is used as color convert material for white LED devices. The white LED device fabricated has an ultra-high color rendering index of 93.9, almost pure white CIE coordinate at (0.332, 0.336) and moderate CCT at 5498 K. The photoluminescence intensity (PL) under constant temperature and alternative condition is both tested to study the thermal stability of the phosphor. The PL intensity shows no obvious change after 3 days of aging;only 4% of PL loss after 10 cycles of 25 degrees C /85 degrees C alternation. Based on its good PL properties and thermal stability, this carbon dots phosphor has great potential for white LED lighting.

关键词： Phosphors Light emitting diodes Thermal stability color Photoluminescence Ethanol Epoxy resins Carbon dots thermal stability white light-emitting diodes color rendering index

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Super powerful LED luminaires with a high color rendering index for lighting systems with combined electric power supply

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SEMICONDUCTOR PHYSICS QUANTUM ELECTRONICS & OPTOELECTRONICS 2022年第1期25卷 97-107页

作者： Pekur, D., V Kolomzarov, Yu, V Sorokin, V. M. Nikolaenko, Yu E. Natl Acad Sci Ukraine V Lashkaryov Inst Semicond Phys 41 Prosp Nauky UA-03680 Kiev Ukraine Natl Tech Univ Ukraine Igor Sikorsky Kyiv Polytech Inst 37 Prosp Peremohy UA-03056 Kiev Ukraine

Considered in this paper are development and creation of high-power LED luminaires with high light efficiency and color rendering index (CRI). As light sources, there used are 6 powerful LED COB (Chip-on-Board) modules CreeCXA 2550, the radiation of which contains quasi-chromatic peaks in the spectral range 600...650 nm. It allows to provide CRI values higher than 92. Features of the improved compact construction of the luminaire with indicated COB modules have been presented. To ensure normal thermal regimes of LED COB modules, a small cooling system based on heat pipes has been created, the optimal dimensions of the structural elements of which have been determined by computer simulation. The results of modeling and experimental studies have shown that the developed and manufactured passive cooling system of LED COB modules provides operation temperature modes (up to 85 degrees C) of light-emitting crystals at the total electric power of COB modules up to 290 W and allows using the luminaires of this type in the systems of continuous artificial illumination with combined power supply. The efficiency of the developed cooling system at some angles to the horizon expands the scope of applying the illumination device.

关键词： energy effective lighting LED color rendering index air cooling heat pipe

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