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1.
Temperature Dependence of Efficiency in GaInN/GaN Light‐Emitting Diodes with a GaInN Underlayer 下载免费PDF全文
Kyurin Kim David S. Meyaard Guan‐Bo Lin E. Fred Schubert Jong Kyu Kim Jaehee Cho 《International Journal of Applied Ceramic Technology》2016,13(2):234-238
The temperature dependence of the efficiency (i.e., temperature‐mediated efficiency droop) in blue light‐emitting diodes (LEDs) is investigated. A GaInN/GaN LED with a GaInN underlayer having an indium mole fraction of 8% shows less temperature dependence of efficiency, compared to the LED without an underlayer. Better carrier confinement in the active region of the LED with a GaInN underlayer is proposed to reduce carrier leakage from the active region at high temperature. The results indicate that the insertion of an underlayer leads to an improvement of the LED's radiative efficiency and its high‐temperature‐tolerant performance. 相似文献
2.
Fatemeh Khodadadian Ali Poursaeidesfahani Zonghan Li J. Ruud van Ommen Andrzej I. Stankiewicz Richard Lakerveld 《化学工程与技术》2016,39(10):1946-1954
The complicated interplay between mass and photon transfer within a photocatalytic reactor calls for an integrated design approach. A model‐based optimization approach for LED‐based photocatalytic reactors is presented. First, a model that describes the distribution of reactants and photons within a photocatalytic reactor is developed. Then, several design variables related to the reactor dimensions and light sources are optimized simultaneously using the photocatalytic degradation of toluene as a model system. The results demonstrate how different formulations of the problem can be used to either minimize the reactor cost or to obtain a specified concentration profile within the reactor. 相似文献
3.
Min‐Suk Jang Wan‐Ho Kim Young‐Rae Kang Sang‐Bin Song Jae‐Pil Kim Jin‐Hyeok Kim 《International Journal of Applied Ceramic Technology》2013,10(4):617-624
Understanding the effect of particle size on the optical properties of phosphor is important to increase packaging efficiency in white light‐emitting diodes (LEDs). We have investigated the effect of particle size (10–20 μm, 20–25 μm, 25–32 μm) on the optical properties of a yellow silicate phosphor adopted in white LEDs. X‐ray diffraction results show negligible modification in crystallinity as the particle size of the yellow silicate phosphor varies, whereas the photoluminescence excitation intensity and quantum yield are enhanced as the particle size increased. LED packages fabricated using phosphors with different mean particle sizes, and their optical properties were analyzed. The radiant flux improved with increasing particle size, whereas the luminous flux increased with decreasing particle size. The effect of immersion on the optical properties of the LED light source has been also measured, and the details are discussed. 相似文献
4.
Far‐Red‐Emitting BiOCl:Eu3+ Phosphor with Excellent Broadband NUV‐Excitation for White‐Light‐Emitting Diodes 下载免费PDF全文
Yongjin Li Zongyan Zhao Zhiguo Song Ronghua Wan Jianbei Qiu Zhengwen Yang Zhaoyi Yin Xuee Liu Qun Liu Yuting Zhou 《Journal of the American Ceramic Society》2015,98(7):2170-2176
Rare‐earth ion‐doped semiconducting phosphor has attracted extensive attention due to the ability to achieve efficient luminescence through the host sensitization. Here, we present a new type red‐emitting Eu3+ ‐doped BiOCl phosphors possessing a broad excitation band in the near‐ultraviolet (NUV) region. Experimental measurements and theoretical calculations confirm that Eu3+ ion dopants result in forming impurity energy level near valence band, and the excellent broadband NUV‐exciting ability of Eu3+ ion is due to the electronic transitions of BiOCl band gap. Moreover, the highest emission intensity of the phosphors is from the 5D0 → 7F4 transition of Eu3+ around 699 nm (far‐red) through whether host excitation or direct Eu3+ ions excitation, which lie in the particular structure of BiOCl crystals. Our results indicate that the Eu3+ ‐doped BiOCl crystals show great potential as red phosphors for white‐light‐emitting diodes. 相似文献
5.
The influence of substitution on the absorption and Luminescence spectra of oligo(phenylenevinylene)s has been studied using distyrylbenzene (DSB) as a model compound. The degree, character, and pattern of substitution was varied systematically, altering the electronic properties of the DSB, the wavelength of the emitted light could be tuned over a range of 100 nm. The syntheses of 6b—h were performed by twofold Wittig Horner‐olefinations of bisphoshonates 1a, b with substituted benzaldehydes 2a—i, 6i via Heck‐reaction of the dibromosulfonylbenzene 3, 6k by Siegrist‐reaction of 4 with N‐phenylbenzaldimine and the Knoevenagel‐reaction of benzyl cyanide with 5 led to 6l . 相似文献
6.
Naresh Kumar Kumawat Zhongcheng Yuan Sai Bai Feng Gao 《Israel journal of chemistry》2019,59(8):695-707
Metal halide perovskite nanocrystals (NCs) have demonstrated great advances for light‐emitting diodes (LEDs) applications, owing to their excellent optical, electrical properties and cost‐effective solution‐processing potentials. Tremendous progress has been made in perovskite NCs‐based LEDs during the past several years, with the external quantum efficiency (EQE) boosted to over 20 %. Recently, metal doping/alloying strategy has been explored to finely tune the optoelectronic properties and enhance material stability of perovskite NCs, leading to further improved device efficiency and stability of the obtained perovskite NCs‐based LEDs. In this review, we summarize recent progress on the metal doping/alloying of perovskite NCs and their applications in LEDs. We focus on the effects of different metal doping strategies on the structural and optoelectronic properties of the perovskite NCs. In addition, several works on high‐performance LEDs based on metal doped/alloyed perovskite NCs with different light emission colours are highlighted. Finally, we present an outlook on employing metal doping/alloying strategies to further improve the device efficiency and stability of LEDs based on perovskite NCs. 相似文献
7.
To develop warm‐white light‐emitting diodes via conversion phosphors, blue light‐emitting diodes are generally combined with mixtures of green and red‐emitting phosphor powders. Generally, the phosphors are provided by resin embedded particle dispersions. Such resin‐based solutions cause several drawbacks with respect to LED lifetime and quality. Therefore, it has been investigated whether the red‐emitting nitride phosphor CaAlSiN3:Eu and the green‐emitting oxidic phosphor YAG:Ce can be cofired to layered ceramic composites. The shrinkage behavior and the composition of the interface in dependence of sintering temperature and the effect of interdiffusion processes at the interface on the luminescence properties were investigated. The formation of secondary phases at the interface in the cofired structures was found to limit the phosphor functionality for the nitride‐based CaAlSiN3:Eu in such composite ceramics. To counteract this, sacrificial interlayers were introduced to produce multilayered ceramics comprising CaAlSiN3:Eu and YAG:Ce for LED lighting applications. It is shown for the first time, that it is possible to sinter layered CaAlSiN3:Eu and YAG:Ce composite ceramics in a pressureless process at moderate sintering temperatures if one uses thin‐film passivated interfaces to reduce luminescence‐disturbing diffusion phenomena. These results demonstrate that diffusion barriers can be suitable means to obtain layered ceramic composites comprising CaAlSiN3:Eu and YAG:Ce in a pressureless sintering process with good optical properties. 相似文献
8.
Lihong Liu Rong‐Jun Xie Wanyuan Li Naoto Hirosaki Yoshinobu Yamamoto Xudong Sun 《Journal of the American Ceramic Society》2013,96(6):1688-1690
A novel Y3?xSi6N11: xCe3+ yellow phosphor was synthesized using the carbothermal reduction and nitridition method at 1550°C for 16 h in this letter. Photoluminescence spectra indicated that the phosphor showed broad excitation spectrum and had strong absorption in range of 350–450 nm. It also gave a broad emission band (Full width at half maximum = 153 nm) centered at 575 nm under 425‐nm excitation. With increasing Ce3+ concentration, the strongest emission intensity was obtained at 5 mol% Ce3+ doping amount and a systematic redshift was observed as the Ce3+ concentration increased. The results indicate that this novel yellow phosphor is a promising candidate for using in blue‐chip‐excited white light–emitting diodes (LEDs). 相似文献
9.
Photoluminescence Properties of Heavily Eu3+‐Doped BaCa2In6O12 Phosphor for White‐Light‐Emitting Diodes 下载免费PDF全文
Jiao Zhang Yanmin Yang Yanzhou Liu Chao Mi Gang Li Boning Han Yi Zhang Hyo Jin Seo 《Journal of the American Ceramic Society》2015,98(5):1567-1573
Heavily Eu3+‐doped BaCa2In6O12 phosphors were prepared by conventional solid‐state reaction, and its structural properties were investigated by means of Rietveld refinement method using an X‐ray source. XRD patterns confirm the hexagonal phase of BaCa2In6O12: Eu3+ phosphors. The obtained spectrum data indicate that the emission spectra of Ba1?xEuxCa2In6O12 samples excited at 393 nm exhibit a series of shaped peaks assigned to the 5D0,1,2,3 →7FJ (J = 0,1,2,3,4) transitions. Luminescence from the higher excited states, such as 5D1, 5D2, and 5D3, were also observed even though the Eu3+ concentration was up to x = 0.4. More importantly, the Ba1?xEuxCa2In6O12 phosphor still emits white luminescence, when the Eu3+ ion concentration is up to x = 0.07 before concentration quenching is observed, which shows that the phosphor is a promising single‐phase phosphor for near ultraviolet (NUV) light‐emitting diodes (LED). Furthermore, the temperature's impact on white luminescent properties was studied. Finally, a white‐light‐emitting diodes (W‐LEDs) fabricated with the Ba0.95Eu0.05Ca2In6O12 phosphor incorporated with an encapsulant in ultraviolet LEDs (λmax = 395 nm) is discussed. 相似文献
10.
折射率为1.6的变色玻璃的研制 总被引:1,自引:0,他引:1
本文总结了折射率为1.6倍的变色玻璃的研制工作,研究了显色工艺与玻璃变色性能的关系,讨论TiO2、Nb2O5、ZrO2对变色玻璃性能的影响。 相似文献
11.
Two benzothiadiazole-based liquid crystalline polyacrylates were synthesized. These polymers revealed a nematic liquid crystal phase and exhibited photoluminescence as well as polarized electroluminescence when incorporated into light-emitting diode applications. The polymers showed dichroic ratios of about 8.3–8.8 in UV-vis absorption and photoluminescence emission. The polymer with vinylene linkages (P2) showed better electroluminescence device performance than that with acetylene linkages (P1). The P2 device emitted red light at 604 nm with a turn-on voltage at 6 V, and a maximum polarized luminance of 235 cd/m2 at 12 V, with an efficiency of 0.09 cd/A and a polarization ratio of 6.5. 相似文献
12.
Photoluminescence of Sr2P2O7:Sm3+ Phosphor as Reddish Orange Emission for White Light‐Emitting Diodes 下载免费PDF全文
Renping Cao Chunyan Cao Xiaoguang Yu Wensheng Li Jianrong Qiu 《International Journal of Applied Ceramic Technology》2015,12(4):755-759
A reddish orange emission Sr2P2O7:Sm3+ phosphor is prepared by the solid‐state reaction method in air, and the crystal structure and luminescence properties of phosphors are investigated. Sr2P2O7:Sm3+ phosphor shows Commission International de I'Eclairage (CIE) chromaticity coordinates (x = 0.5753, y = 0.4147). White light‐emitting diodes (W‐LEDs) fabricated using Sr2P2O7:Sm3+ phosphor etc. show CIE chromaticity coordinates (x = 0.3471, y = 0.3124). These results indicate that Sr2P2O7:Sm3+ phosphor could be a potential suitable reddish orange emitting phosphor candidate for W‐LEDs with excitation of a ~400 nm n‐UV LED chip. 相似文献
13.
The diameter dependence of the refractive index of as-formed glass fibers is examined. It is shown that the measured results on fibers of a soda–lime–silica glass can be satisfactorily explained by combining three factors: the diameter dependence of the cooling rate, the cooling rate dependence of the fictive temperature, and the dependence of glass properties on its fictive temperature. 相似文献
14.
N. V. Nikonorov E. I. Panysheva I. V. Tunimanova A. V. Chukharev 《Glass Physics and Chemistry》2001,27(3):241-249
The influence of the main components (SiO2, Al2O3, ZnO, and Na2O) of a photothermorefractive glass matrix and Br–ions on the change in the refractive index is studied in the course of photothermoinduced crystallization in glasses. The optimum concentrations of these components at which the change in the refractive index is maximum are determined. The regularities revealed are explained within the modern concepts of the structure of polychromatic glasses and the nature of the photothermorefractive effect. 相似文献
15.
Luminescence Properties and Energy‐Transfer Behavior of a Novel and Color‐Tunable LaMgAl11O19:Tm3+, Dy3+ Phosphor for White Light‐Emitting Diodes 下载免费PDF全文
Xin Min Minghao Fang Zhaohui Huang Yan'gai Liu Chao Tang Xiaowen Wu 《Journal of the American Ceramic Society》2015,98(3):788-794
Novel LaMgAl11O19:Tm3+, Dy3+ phosphors were prepared utilizing a high‐temperature solid‐state reaction method. The phase formation, luminescence properties, energy‐transfer mechanism from the Tm3+ to the Dy3+ ions, the thermal stability, and CIE coordinates were investigated. When excited at 359 nm, the LaMgAl11O19: xTm3+ phosphors exhibit strong blue emission bands at 455 nm. After codoping with Dy3+ and excitation at 359 nm, the LaMgAl11O19:0.03Tm3+, yDy3+ phosphors emitted white light consisting of the characteristic emission peaks of Tm3+ and Dy3+. The Dy3+ emission intensity increased with the Dy3+ concentration due to the energy transfer from Tm3+ to Dy3+, and concentration quenching due to the high Dy3+ doping concentration (y = 0.1 mol) did not occur. The calculation of the CIE coordinates of the LaMgAl11O19:Tm3+, yDy3+ phosphors revealed the tunability of the emission color from blue to bluish‐white and to white by changing the excitation wavelength and the doping concentration. An energy transfer from Tm3+ to Dy3+ by dipole–dipole interaction was confirmed by the decay curve, lifetime, and energy‐transfer efficiency measurements. When excited at 359 nm, the LaMgAl11O19:Tm3+, Dy3+ phosphor also showed good thermal stability, suggesting that it can be used in white LEDs excited by a GaN‐based ultraviolet LED. 相似文献
16.
Silvia Di Lodovico Firas Diban Paola Di Fermo Morena Petrini Antonella Fontana Mara Di Giulio Adriano Piattelli Simonetta DErcole Luigina Cellini 《International journal of molecular sciences》2022,23(13)
Innovative non-antibiotic compounds such as graphene oxide (GO) and light-emitting diodes (LEDs) may represent a valid strategy for managing chronic wound infections related to resistant pathogens. This study aimed to evaluate 630 nm LED and 880 nm LED ability to enhance the GO antimicrobial activity against Staphylococcus aureus- and Pseudomonas aeruginosa-resistant strains in a dual-species biofilm in the Lubbock chronic wound biofilm (LCWB) model. The effect of a 630 nm LED, alone or plus 5-aminolevulinic acid (ALAD)-mediated photodynamic therapy (PDT) (ALAD-PDT), or an 880 nm LED on the GO (50 mg/l) action was evaluated by determining the CFU/mg reductions, live/dead analysis, scanning electron microscope observation, and reactive oxygen species assay. Among the LCWBs, the best effect was obtained with GO irradiated with ALAD-PDT, with percentages of CFU/mg reduction up to 78.96% ± 0.21 and 95.17% ± 2.56 for S. aureus and P. aeruginosa, respectively. The microscope images showed a reduction in the cell number and viability when treated with GO + ALAD-PDT. In addition, increased ROS production was detected. No differences were recorded when GO was irradiated with an 880 nm LED versus GO alone. The obtained results suggest that treatment with GO irradiated with ALAD-PDT represents a valid, sustainable strategy to counteract the polymicrobial colonization of chronic wounds. 相似文献
17.
The phenomena accompanying the effect revealed earlier that manifests itself as a peak of the intensity of light scattered at an angle of 90° and is universally observed in the glass transition range of oxide glasses are investigated. It is shown that the development of this peak is attended by the appearance of the diffraction pattern in the vicinity of the light beam passing through the sample. This effect is associated with the formation of ngratings in the sample bulk due to the interaction of a low-intensity laser radiation with a highly unstable glass structure. The glass samples with a spatially modulated refractive index have been prepared by the quenching technique. 相似文献
18.
Seunggu Kang§ Hongy Lin Delbert E. Day 《Journal of the American Ceramic Society》1996,79(10):2633-2636
Glass fibers pulled from multihole bushings can have a slight difference in thermal history that causes a distribution in the refractive index that can be narrowed by annealing the fibers. The kinetics for the initial stage change in refractive index for fiber annealed between 300° and 500°C are best described by a second-order reaction with an activation energy of 120° 17 kj/mol. The improved uniformity in refractive index for annealed fibers is indicated by a decrease in the half-height width of the optical transmission versus temperature curve for glass fiber immersed in a liquid. The standard deviation in the refractive index of glass fibers with a bimodal distribution in diameter decreases from 8 × 10-4 ≤0.0002 to 4 × 10-4 0.0002 after the fibers are annealed at 400°C for 1 h. 相似文献
19.
Enhanced Fluorescence and Local Vibrational Mode in Near‐White‐Light‐Emitting ZnO:Mg Nanorods System 下载免费PDF全文
Rednam Udayabhaskar Balasubramanian Karthikeyan 《Journal of the American Ceramic Society》2015,98(6):1807-1811
We report exciton and phonon properties of ZnO:Mg nanorods of different Mg doping concentration. X‐ray diffraction studies (XRD) confirm the growth of wurtzite phase ZnO nanostructures. XRD reveals doping‐induced shift in peaks and formation of secondary phase related to Mg. Optical properties of the prepared nanorods are investigated by using UV‐Visible absorption and photoluminescence spectroscopic techniques. Optical absorption studies show strong free excitonic absorption of ZnO and extra absorption bands related to the defect centers of the secondary phase (MgO) formed after Mg doping. Photoluminescence studies show sharp band in UV region and defects‐related broad band emission in the visible range. Gaussian‐fitted photoluminescence spectra show that the emission is composed of free exciton recombination and its longitudinal optical (LO) phonon replica. In addition, Mg‐related local vibrational mode observed in Raman and FTIR spectra after Mg doping, indicates the incorporation of Mg into the lattice positions of wurtzite ZnO. 相似文献