Journal of Materials Chemistry C
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2017
·Vol. 5
·期 39
·10241-10250
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IF 5.256
Mengmeng Zhu,Yuexiao Pan,Luqing Xi,Hongzhou Lian,Jun Lin
Mn4+-activated red phosphors have attracted considerable attention as promising red components in the spectra of white light emitting diodes (WLEDs) to achieve warm white light with superior performance. Herein, a novel red phosphor based on Mn4+-doped dodec-fluoride Li3Na3Al2F12:Mn4+ (LNAF:Mn) with microcubic morphology was obtained at room temperature. To elucidate the underlying relationship between the crystal structure and photoluminescence of LNAF:Mn, a phosphor LiNa2AlF6:Mn4+ with similar composition has been prepared, and their morphology and optical properties were comparatively investigated. The emission of the red phosphor LNAF:Mn is blue shifted compared to LiNa2AlF6:Mn4+ suggesting that the chromaticity coordinates of LANF:Mn are closer to the ideal red point (0.67, 0.33). The luminescence properties of LNAF:Mn have been improved by optimizing the synthetic conditions. This work exhibits a strategy to explore a novel Mn4+-doped fluoride except for the identified hexa-fluorides. Employing the as-prepared red LNAF:Mn as a red component, a high-performance WLED with a correlated color temperature (CCT) of 3874 K and a color rendering index (CRI) of 90.6 was obtained. This suggests the phosphor is a potential commercial red phosphor in warm WLEDs.
研究领域:
材料科学
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光学工程
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高影响因子
Journal of Materials Chemistry C
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2017
·Vol. 5
·期 36
·9255-9263
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IF 5.256
Luqing Xi,Yuexiao Pan,Mengmeng Zhu,Hongzhou Lian,Jun Lin
A kind of red-emitting phosphor NaKSnF6:Mn4+ (NKSF:Mn) has been obtained from NaF and KF with a certain molecular ratio in HF solution at room temperature. The phosphor NKSF:Mn exhibits superior optical properties including high color purity with narrow-band emissions as well as better chromaticity coordinates compared to the red phosphors Na2SnF6:Mn4+ (NSF:Mn) and K2SnF6·H2O:Mn4+ (KSFH:Mn). The composition and structure of NKSF:Mn have been identified by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The formation mechanism of NKSF:Mn is discussed and the morphology, thermal stability, and optical properties of NKSF:Mn have been investigated. The luminescence intensity of NKSF:Mn has been improved by optimizing synthetic parameters. A white light-emitting diode (WLED) fabricated using a blue GaN chip, a yellow YAG:Ce phosphor, and the as-prepared red phosphor NKSF:Mn exhibits superior warm white light with a color rendering index (CRI) of 90.3 at a correlated color temperature (CCT) of 3746 K.
研究领域:
材料科学
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光学工程
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高影响因子
Nanoscale
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2018
·Vol. 10
·期 47
·22237-22251
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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
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光学工程
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DOI
PubMed
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
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2020
·Vol. 103
·期 12
·6901-6912
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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
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光学工程
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DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
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2021
·Vol. 32
·期 23
·27513-27523
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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
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光学工程
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DOI
高影响因子
Journal of Materials Chemistry C
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2019
·Vol. 7
·期 20
·6077-6084
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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
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光学工程
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高影响因子
Journal of Materials Chemistry C
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2020
·Vol. 8
·期 13
·4408-4420
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IF 7.059
Shaoying Wang,Balaji Devakumar,Qi Sun,Jia Liang,Liangling Sun,Xiaoyong Huang
Inorganic phosphors with broadband near-ultraviolet (near-UV) excitation and efficient visible emission are highly important for fabricating high-performance near-UV-pumped white light-emitting diodes (LEDs). Herein, we report on novel efficient near-UV-excitable Ce3+/Tb3+ ion co-activated Ca2YHf2Al3O12 (CYHA) green-emitting garnet phosphors, which were successfully prepared through a high-temperature solid-state reaction process. X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, photoluminescence, CIE color coordinates, the internal and external quantum efficiency, and temperature-dependent emission spectra were used to characterize the samples. Interestingly, due to the efficient energy transfer from Ce3+ to Tb3+ ions in CYHA, the CYHA:Ce3+,Tb3+ samples presented a wide excitation band in the 370–470 nm region peaking around 408 nm owing to the 4f–5d transition of Ce3+ ions, and under 408 nm excitation they showed intense characteristic sharp green emission around 543 nm corresponding to the 5D4 → 7F0–6 transitions of Tb3+ ions. The energy transfer mechanism from Ce3+ to Tb3+ ions was ascribed to the quadruple–quadruple interaction, and the energy transfer efficiency reached as high as 93.2%. Notably, the composition-optimized CYHA:0.03Ce3+,0.6Tb3+ sample exhibited a high internal quantum efficiency (IQE) of 78.5% and external quantum efficiency (EQE) of 56%, which were much higher than those of the Tb3+ singly-activated CYHA:0.6Tb3+ sample (IQE = 8%, EQE = 2.2%). Finally, a prototype white LED device was made by combining a 400 nm near-UV-emitting LED chip with a phosphor blend of the as-prepared CYHA:0.03Ce3+,0.6Tb3+ green phosphors, commercial BaMgAl10O17:Eu2+ blue phosphors and commercial CaAlSiN3:Eu2+ red phosphors, which emitted bright warm-white light with good CIE chromaticity coordinates of (0.391, 0.356), a low correlated color temperature of 3528 K and a high color rendering index of 92.3 under 120 mA driving current. This work opens up new opportunities for the development of efficient color converters toward near-UV-pumped warm-white LEDs with high color rendering index.
研究领域:
材料科学
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光学工程
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高影响因子
DALTON TRANSACTIONS
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2021
·Vol. 51
·期 2
·645-654
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IF 4.39
Qinghong Meng,Guoying Zhao,Qi Zhu,Xiaodong Li,Xudong Sun,Ji-Guang Li
Synergistic doping of the metastable Gd3Al5O12:Ce garnet with a Ca2+/Hf4+ pair and Sc3+ to form Gd2.97−xCaxHfxScyAl3O12:0.03Ce (x = 0.5–2.0, y = 0.0–1.5, x + y = 2.0) solid solution was conducted for the structural stabilization and photoluminescence manipulation. The site selection of Ca2+/Hf4+/Sc3+ dopants and the effects of doping on the crystal structure, local coordination, band structure and Ce3+ luminescence were revealed in detail with the results of XRD, Rietveld refinement, TEM, and UV-Vis/photoluminescence spectroscopy. A decrease in Ca2+/Hf4+ and an increase in the Sc3+ content were observed to shrink the lattice, widen the bandgap of the garnet host, red-shift the excitation/emission wavelength, broaden the emission band and shorten the fluorescence lifetime of Ce3+. The spectral changes were rationalized by considering the local coordination and crystal field splitting of the Ce3+ 5d energy level. Application of typical Gd0.97Ca2Hf2Al3O12:0.03Ce (x = 2.0, y = 0) cyan and Gd2.47Ca0.5Hf0.5Sc1.5Al3O12:0.03Ce (x = 0.5, y = 1.5) greenish-yellow phosphors in w-WLED lighting produced low correlated color temperatures of ∼3842 and 3514 K, high color rendering indices of ∼88 and 93 and favorable luminous efficacies of ∼32.9 and 14.7 lm/W under the excitation of 395 nm n-UV and 450 nm blue LED chips, respectively.
研究领域:
材料科学
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光学
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PubMed
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
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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
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光学工程
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DOI
高影响因子
JOURNAL OF RARE EARTHS
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2025
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IF 7.2
Ya Li,Yunxiao Ma,Hui Yu,Ming Yang,Xiangting Dong,Zhijia Lv
Due to the difficulty of luminescence intensity optimization and color control, the research on the regulatable warm white light emitting devices and fluorescent labels for multi-color detection is ongoing. The Ln 3+ -Bi 2 (PTA) 3 /Bi 2 O 3 phosphors with rod-shaped structure were prepared by one-step hydrothermal method, and the incorporation of Bi 2 O 3 and terephthalic acid (PTA) ligand effectively magnifies the absorption ability for the photons to enhance the emission intensity. The mono lanthanide-doped Dy-Bi 2 (PTA) 3 /Bi 2 O 3 exhibits pure cool white light, and it can be transformed to warm white light with the co-doped Eu 3+ amount increasing. Eu 3+ -Tb 3+ -Bi 2 (PTA) 3 /Bi 2 O 3 can emit red and green light, which is used as the multi-color fluorescence labeling, and the mixed formed yellow light fills the blank of the yellow lighting device.
研究领域:
材料科学
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光学
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生物医学工程
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DOI
高影响因子
DALTON TRANSACTIONS
·
2017
·Vol. 46
·期 40
·13835-13844
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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
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光学工程
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PubMed
高影响因子
MATERIALS RESEARCH BULLETIN
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2021
·
IF 4.641
Yanzhen Yin,Zhen Wang,Maochen Zhu,Yue Zhang,Jianhong Li,Chao Dou,Shijia Sun,Bing Teng,Yang Che,Degao Zhong
A single-phased warm white phosphor of α-Sr 2 V 1.98 P 0.02 O 7 : 0.5 % Eu 3+ with low correlated color temperature (CCT) and high color rendering index (CRI) was synthesized by high temperature solid phase method. By changing the ratio of PO 4 3− /VO 4 3− , the emission intensity of VO 4 3− and the energy transfer efficiency of VO 4 3− →Eu 3+ can be effectively tuned, and the full-spectrum warm white light emission of phosphors in the range of 400−700 nm can be realized. Moreover, the temperature-dependent emission spectra and thermal quenching properties were investigated in detail. On this basis, the WLED prototype devices were packaged with the synthesized phosphors α-Sr 2 V 1.98 P 0.02 O 7 : 0.5 % Eu 3+ and 365 nm near-ultraviolet (NUV) chips and high-quality warm white light emission with CCT = 3188 K and CRI Ra = 93.5 were achieved. These findings provide new insights into exploring single-phased white phosphors for NUV-pumped warm w-LEDs with high CRI property and low CCT value.
研究领域:
材料科学
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光学工程
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高影响因子
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