Nanoscale
·
2018
·Vol. 10
·期 47
·22237-22251
·
IF 7.233
Guo-Hui Pan,Huajun Wu,Shuai He,Liangliang Zhang,Zhendong Hao,Xia Zhang,Jiahua Zhang
The most common yellow phosphor for wLEDs, Y3Al5O12:Ce3+ (YAG:Ce3+), suffers from a deficiency of red in its spectral content of light. In this paper, a new strategy is provided to tailor the Ce3+ spectral profile through surface-located dye molecules of ATTO-Rho101, which feature intense, broad absorption in the green-yellow spectral region of Ce3+ emission as well as bright red emission. Sphere-shaped and highly dispersed micrometer and nanometer-sized YAG:Ce3+ (micro/nano-YAG:Ce3+) was synthesized through a modified solvothermal method. Surface SiO2 coating and simultaneous dye embedding were performed on the solvothermally derived YAG:Ce3+, heat-treated micro-YAG:Ce3+ and commercial phosphors. Efficient radiative transfer/reabsorption from Ce3+ in the inner core of YAG to the dye molecules in the SiO2 outer shell, irrespective of the size of the phosphors, was demonstrated in the accumulated YAG:Ce3+@SiO2 + dye powder upon blue light excitation; this enhanced its red emission. Fluorescence microscopy was demonstrated to be a powerful tool to identify the reabsorption phenomenon of the powdered materials. Packaging the heat-treated micro-YAG:Ce3+@SiO2 + dye phosphors on blue LED chips yielded a warm wLED (Ra ∼ 93), but an Ra of only ∼79 was obtained for the wLED with commercial YAG:Ce3+@(SiO2 + dye)5 due to the low concentration of phosphors dispersed in the epoxy resin and the resulting decreased reabsorption by dye molecules. Surface-protonated amine species were found to induce Ce3+ → Ce4+ oxidation upon activation by heating or photoirradiation and then quench the photoluminescence (PL) of micro-YAG:Ce3+ even after surface modification by SiO2, YAG or being embedded in an epoxy resin matrix. High calcination temperatures greatly improved the PL stability of micro-YAG:Ce3+ through the removal of surface-capped species. The dye in the silica matrix showed high stability against heating and irradiation due to the so-called “caging effects”; however, decreased photo-stability was found in commercial YAG:Ce3+@(SiO2 + dye)5 due to the incomplete and/or loose SiO2 layer grown during multiple surface modifications.
研究领域:
材料科学
·
光学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2020
·Vol. 103
·期 12
·6901-6912
·
IF 3.502
Qiyun Wu,Chenxing Liao,Jinquan Pan,Xinyu Ye,Weixiong You,Libin Xia
It has been one of the hot issues to prepare the red-emitting Mn 4+ -doped fluoride phosphors with highly efficient and waterproofness for warm white-light-emitting diodes (WLEDs) by the green and environmentally friendly method. Herein, we design a novel green molten salt route to synthesize K 2 SiF 6 :Mn 4+ red powder using molten NH 4 HF 2 salt instead of HF liquor as the reaction medium. The results show that KMnO 4 and MnF 2 could produce Mn 4+ in NH 4 HF 2 molten salt through a reduction reaction, and the resulting Mn 4+ -doped K 2 SiF 6 exhibited a bright red emission peaked at 632 nm under blue light excitation. The luminescence intensity of the as-obtained product after immersing into water for 24 hours maintain nearly 100% of that before soaking and emission peak shape remains unchanged. The thermal stability of the sample was evaluated by temperature-dependent luminescence spectral intensity during heating and cooling. Furthermore, a warm white-light-emitting diodes (WLEDs) with an excellent color rendering index (Ra = 87.1), lower correlated color temperature (CCT = 3536K), and high luminous efficacy (116.99 lm·W −1 ) was fabricated based on blue chip and K 2 SiF 6 :Mn 4+ and commercial yellow phosphor (Y 3 Al 5 O 12 :Ce 3+ ).
研究领域:
材料科学
·
光学工程
✓ 已验证
DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
·
2021
·Vol. 32
·期 23
·27513-27523
·
IF 2.478
He Youyi,Liu Jun,Gao Yalei,Yan Lijuan,Lv Fengzhen,Liu Fuchi,Long Lizhen
Mn 4+ -activated phosphors have become a hotspot in the development of inorganic red phosphors due to the fascinating photoluminescent properties. Herein, the synergetic manipulation of the flux effect and charge compensation was employed to improve the performance of Mn 4+ -activated CaAl 12 O 19 red phosphors. The crystallinity was improved by appropriate Zn 2+ -doping, while nonradiative transition between Mn 4+ ions is reduced by charge compensation of the formation of Mn 4+ –Mg 2+ pairs with Mg 2+ dopants. Thus, the emission of Mn 4+ -activated CaAl 12 O 19 red phosphors has been remarkably enhanced. The low probability of nonradiative transition between Mn 4+ ions was demonstrated by the thermal stability analysis. To depict the luminescent process, the crystal-field strength ( D q ), and Racah parameters ( B and C ) were calculated to determine the sequence of the energy levels. Meanwhile, the warm WLEDs with high CRI and low CCT were obtained using the prepared phosphors as red-emitting composition. Our results clearly suggested that the synergetic strategy by combining the flux effect and charge compensation is an effective method to enhance the luminescence of CaAl 12 O 19 :Mn 4+ , and CaAl 12 O 19 :Mn 4+ /Zn 2+ /Mg 2+ red-emitting phosphors, which have potential application value in warm WLEDs.
研究领域:
材料科学
·
光学工程
✓ 已验证
DOI
高影响因子
Journal of Materials Chemistry C
·
2019
·Vol. 7
·期 20
·6077-6084
·
IF 6.641
Chunyan Jiang,Lihua Li,Mikhail G. Brik,Litian Lin,Mingying Peng
The poor moisture-resistant property of the commercial narrow band red-emitting K2SiF6:Mn4+ phosphor restricts its practical application in high performance warm WLEDs. Herein, we report epitaxial growth via simple ethanol-induced deposition to enhance the luminescence and moisture resistance of K2SiF6:Mn4+. Specifically, an appropriate amount of ethanol at the end of the synthesis leads to epitaxial growth of a K2SiF6:Mn4+ shell. The resultant K2SiF6:Mn4+@K2SiF6:Mn4+ presents higher photoluminescence intensity due to a high Mn4+ critical concentration in the K2SiF6:Mn4+ epitaxial shell. Furthermore, the epitaxial growth of the K2SiF6 shell on K2SiF6:Mn4+ is designed to conquer the moisture resistance. As expected, the formed K2SiF6:Mn4+@K2SiF6 retains 82% of the initial emission intensity after being immersed in water for 4 h and 90% after being exposed to high temperature and humidity (85 °C, 85%) for 10 days. By employing K2SiF6:Mn4+@K2SiF6 as a red phosphor, a packaged white LED exhibits excellent performance with a CRI of 96.5, a CCT of 2879 K and a luminous efficacy of 119.74 lm W−1. More importantly, this fabricated WLED device retains high luminous efficacy and undergoes minor chromatic coordinate changes when aged at high temperature and humidity (85 °C, 85%). Therefore, these findings not only illustrate the effect of ethanol addition on the photoluminescence intensity of Mn4+ doped phosphors in the synthesis process, but also provide a facile strategy to improve the moisture resistance of K2SiF6:Mn4+ for warm WLEDs in the future.
研究领域:
材料科学
·
光学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2019
·
IF 4.175
Yuanjing Wang,Yayun Zhou,Enhai Song
Mn 4+ -activated fluoride red phosphors have a bright prospect for improving the warm white light-emitting diodes (W-LEDs) performances, whereas there remains some challenges in synthesis, such as reducing the consumption of toxic HF and improving Mn 4+ doping efficiency. Herein, a new phosphor (NH 4 ) 2 NaScF 6 :Mn 4+ (NNSFM) was synthesized by an ammonium salt conversion method, which can effectively reduce HF consuming, enhance reaction rate and doping efficiency. The synthesis mechanism, luminescence properties and W-LEDs performances of the as-synthesized NNSFM have been investigated. Moreover, the lattice structure and doping position have been investigated in detail by the density functional calculations (DFT), which show that Mn 4+ could occupy the Sc 3+ crystallographic site in this structure and simultaneously produce a Na vacancy ( V Na ' ) for charge compensation. Using the NNSFM as red-light component, a warm W-LED device with a high color rendering index (CRI, Ra = 80.6) and low correlated color temperature (CCT = 3006 K) has been achieved. This work presents a new Mn 4+ doped fluoride red phosphor and also develops an environmentally friendly strategy for synthesizing Mn 4+ doped fluoride phosphors.
研究领域:
材料科学
·
光学工程
✓ 已验证
DOI
高影响因子
DALTON TRANSACTIONS
·
2017
·Vol. 46
·期 40
·13835-13844
·
IF 4.029
Luqing Xi,Yuexiao Pan,Mengmeng Zhu,Hongzhou Lian,Jun Lin
A novel red phosphor, NaHF2:Mn4+ (NHF:Mn), was obtained via substituting Na+ located at the center of the octahedron coordinated with six F− ions with Mn4+ in the host lattice of NHF. The phase purity and the exact composition of the obtained NHF:Mn were confirmed by X-ray powder diffraction (XRD), Rietveld refinement, energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and infrared (IR) spectroscopy, respectively. The luminescence intensity of NHF:Mn was enhanced by optimizing the synthetic conditions. A series of warm white light-emitting diodes (WLEDs) with a color rendering index (CRI) higher than 88.0 and correlated color temperatures (CCT) between 3146 and 5172 K were obtained by encapsulating the as-prepared red phosphor NHF:Mn with the yellow one Y3Al5O12:Ce3+ (YAG:Ce) on blue chips. The advantage of the synthetic strategy to obtain NHF:Mn can be extended to develop novel Mn4+ doped red phosphors via substituting for central ions with unequal electric charge in the centers of octahedra.
研究领域:
材料科学
·
光学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2016
·
IF 3.014
Cheng Yang,Zhongfang Zhang,Guangcai Hu,Rui Cao,Xiaojuan Liang,Weidong Xiang
Currently, the non-rare-earth Mn 4+ -activated oxide red phosphor is of great interest as color converter for warm white light-emitting diodes (W-LEDs), owing to its admirable luminescent properties and low price. Herein, a novel blue-light activated Ca 14 Zn 6 Ga 10 O 35 :Mn 4+ (CZG:Mn 4+ ) phosphor, exhibiting strong red emission attributed to Mn 4+ : 2 E g → 4 A 2g spin-forbidden transition in region of 650–750 nm under 462 nm excitation, is successfully synthesized through a traditional solid-state reaction route in air. Subsequently, the microstructure and luminescent performance of this red-emitting phosphor are discussed in detail. The crystal field strength ( Dq ) and the Racah parameters ( B and C ) are carefully calculated to estimate the nephelauxetic effect of Mn 4+ suffering from the CZG host lattice. In addition, the concentration quenching and thermal quenching characteristics are also systematically investigated. After incorporating CZG:Mn 4+ and commercial Y 3 Al 5 O 12 :Ce 3+ (Ce:YAG) phosphors into a blue LED device, warm white light with high color rendering index and low correlated color temperature is successfully achieved. Therefore, the CZG:Mn 4+ phosphor can serve as color converter for use in warm W-LED applications.
研究领域:
材料科学
·
光学工程
✓ 已验证
产品关联
DOI
高影响因子
RSC Advances
·
2017
·Vol. 7
·期 79
·50396-50402
·
IF 3.108
Shijie Qiu,Hengwei Wei,Mengmeng Wang,Shuai Zhang,Yang Zhou,Ling Xu,Xiaoming Wang,Huan Jiao
A novel ternary-alkaline red emitting fluoride phosphor K2NaGaF6:Mn4+ was successfully synthesized through co-precipitation method. The crystal structure, morphology, electronic band structure and luminescence properties of K2NaGaF6:Mn4+ phosphors were investigated in details by using Rietveld refinement of X-ray diffraction data, scanning electron microscopy (SEM), density functional theory (DFT) calculation and different reaction parameters. The K2NaGaF6 host has a cubic unit cell with the space group Fmm and lattice parameters of a = 8.2577 (4) Å, Z = 4, Vcell = 563.08 (8) Å3. Under blue light excitation, Mn4+ activated K2NaGaF6 exhibits a bright narrow-band red emission. The PL properties of the K2NaGaF6:Mn4+ red phosphors were optimized with different Mn4+ concentrations and aging times. A warm-white LED device was fabricated using a blue LED chip combined with commercial yellow YAG:Ce3+ phosphor and synthesized K2NaGaF6:Mn4+ red phosphor. The color rendering index (CRI, Ra = 81.6) and corresponding color temperature (CCT = 3643 K) easily reached the commercial warm white light LED standards (Ra > 80 and CCT < 4000 K). All these results indicate that K2NaGaF6:Mn4+ phosphor would be a suitable red phosphor candidate for warm-white LED applications.
研究领域:
材料科学
·
光学
·
电子工程
✓ 已验证
产品关联
DOI
高影响因子
Journal of Materials Chemistry C
·
2016
·Vol. 4
·期 13
·2480-2487
·
IF 5.066
E. H. Song,J. Q. Wang,S. Ye,X. F. Jiang,M. Y. Peng,Q. Y. Zhang
A novel red fluoroaluminate phosphor, cryolite Na3AlF6:Mn4+, has been designed and synthesized via a facile two-step method at room temperature. Under blue light excitation, it exhibits intense sharp line red fluorescence (∼630 nm) with high color purity. The crystal structure, morphology and doping concentration of the samples were characterized in detail using X-ray diffraction (XRD), scanning electron microscopy (SEM) and ICP-AES. The influence of synthesis conditions, raw materials and doping concentration on crystal structure and photoluminescence (or decay behavior) has been investigated carefully. The optimal composition, Na3AlF6:1.58%Mn4+, shows a bright red light and excellent thermal stability (∼99.93% of the emission intensity at 200 °C relative to 23 °C) upon ∼467 nm blue light excitation. A warm high-power white LED with a high color rendering index (Ra = 92.7 and R9 = 94) and low color temperature (CCT = 3903 K) was fabricated based on the blue InGaN chip, commercial yellow phosphor YAG:Ce3+ and red phosphor Na3AlF6:Mn4+.
研究领域:
材料科学
·
光学工程
✓ 已验证
DOI
高影响因子
Journal of Materials Chemistry C
·
2017
·Vol. 5
·期 11
·2910-2918
·
IF 5.256
T. T. Deng,E. H. Song,J. Sun,L. Y. Wang,Y. Deng,S. Ye,J. Wang,Q. Y. Zhang
Herein, a new red phosphor Na3GaF6:Mn4+ has been designed and synthesized by a facile two-step co-precipitation method at room temperature. Single crystal X-ray diffraction analysis reveals that the fluoride Na3GaF6 crystallizes in the P2(1)/n space group with a = 5.4760 Å, b = 5.6862 Å, c = 7.9009 Å, β = 90.309°, and z = 2. Upon blue or UV light excitation, the obtained phosphor Na3GaF6:Mn4+ emits intense and pure red fluorescence. The effects of raw materials, doping concentration and environmental temperature on its luminescence properties and crystal structure have been investigated and discussed in detail. Such a newly synthesized red phosphor shows excellent anti-thermal quenching behavior (∼118.8% of emission intensity at 150 °C relative to 25 °C) and good color stability upon blue light (∼467 nm) excitation. By using the Na3GaF6:Mn4+ phosphor as a red light component, a high-power stable warm white light-emitting diode (WLED, Ra = 81, CCT = 2966 K, luminous efficacy = 56.73 lm W−1) was fabricated, further evidencing the potential of the as-synthesized Na3GaF6:Mn4+ phosphor for white LED applications.
研究领域:
材料科学
·
光学工程
✓ 已验证
产品关联
DOI
高影响因子
Journal of Materials Chemistry C
·
2019
·Vol. 7
·期 26
·7906-7914
·
IF 6.641
Jun Gao,Haomiao Zhu,Renfu Li,Decai Huang,Benlong Luo,Wenwu You,Jianxi Ke,Xiaodong Yi,Xiaoying Shang,Jin Xu,Zhonghua Deng,Li Xu,Wang Guo,Xueyuan Chen
Mn4+-Doped fluoride red phosphors with excellent moisture-resistant properties and high emission efficiency are highly desired for warm white LEDs and wide gamut liquid crystal displays. Herein, we synthesized a K2NaGaF6:Mn4+ red phosphor through a co-precipitation method at room temperature. The crystallographic structure of the K2NaGaF6 host was determined based on single crystal X-ray diffraction data for the first time. A high internal photoluminescence quantum yield of 82% was achieved for the 1.81 at% K2NaGaF6:Mn4+ sample. Through low-temperature and high-resolution spectroscopic analysis, we revealed that Mn4+ ions occupy at least four distinct sites in the K2NaGaF6 crystal. One of them is assigned to the Ga3+ site with high Oh site symmetry and the other three ones possess low non-centrosymmetric site symmetries. By employing 5.51 at% K2NaGaF6:Mn4+ as a red phosphor, a warm white LED with a low correlated color temperature of 3760 K, a high color rendering index of 92 (Ra) and a luminous efficacy of 156 lm W−1 was packaged. Aging tests at 85 °C and 85% relative humidity on the fabricated LEDs demonstrated that K2NaGaF6:Mn4+ has a better moisture-resistant property than that of the popular K2SiF6:Mn4+ phosphor. These findings demonstrate the great potential of K2NaGaF6:Mn4+ as a highly efficient red phosphor with excellent moisture-resistant performance.
研究领域:
材料科学
·
光学工程
✓ 已验证
产品关联
DOI
高影响因子
Science China-Technological Sciences
·
2017
·Vol. 60
·期 10
·1458-1464
·
IF 1.719
Zhu YiWen,Liu Yong,Huang Lin,Xuan TongTong,Wang Jing
Red phosphor K 2 LiAlF 6 :Mn 4+ has been synthesized by a cation-exchange method in HF solution. To optimize their optical properties, phosphors were synthesized using different reaction conditions. The K 2 LiAlF 6 :0.5%Mn 4+ synthesized at 20°C for 4 h shows the highest luminescence intensity. The temperature-dependent emission intensity of the phosphor was investigated, and it was found to exhibit good thermal stability, making it a promising red phosphor candidate for warm WLEDs.
研究领域:
材料科学
·
光学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）