A series of YAG:Ce,Mn transparent ceramics were prepared via a solid-state reaction-vacuum sintering method.The effects of various Mn^2+–Si4+pair doping levels on the structure,transmittance,and luminescence properti...A series of YAG:Ce,Mn transparent ceramics were prepared via a solid-state reaction-vacuum sintering method.The effects of various Mn^2+–Si4+pair doping levels on the structure,transmittance,and luminescence properties were systematically investigated.These transparent ceramics have average grain sizes of 10–16μm,clean grain boundaries,and excellent transmittance up to 83.4%at 800 nm.Under the excitation of 460 nm,three obvious emission peaks appear at 533,590,and 745 nm,which can be assigned to the transition 5 d→4 f of Ce^3+and 4 T1→6 A1 of Mn^2+.Thus,the Mn^2+–Si4+pairs can effectively modulate the emission spectrum by compensating broad orange-red and red spectrum component to yield high quality warm white light.After the optimized YAG:Ce,Mn transparent ceramic packaged with blue light-emitting diode(LED)chips,correlated color temperature(CCT)as low as 3723 K and luminous efficiency(LE)as high as 96.54 lm/W were achieved,implying a very promising candidate for application in white light-emitting diodes(WLEDs)industry.展开更多
Phosphor-in-glass(PiG)is a potential color convertor for high power WLEDs.A novel glass matrix with advanced performance is still a challenge.Recently,Eu^(3+)doped glass matrix has attracted much consideration mainly ...Phosphor-in-glass(PiG)is a potential color convertor for high power WLEDs.A novel glass matrix with advanced performance is still a challenge.Recently,Eu^(3+)doped glass matrix has attracted much consideration mainly due to its red compensation.A new borophosphate matrix to realize Eu^(3+)red light was designed in the Na_(2)O-ZnO-P_(2)O_(5)-B_(2)O_(3)-Eu_(2)O_(3)system.Meanwhile,a series of PiGs composed of different concentrations of Y3Al5O12:Ce phosphor and the matrix were also fabricated by re-sintering.The crystallization of Eu^(3+)based phosphate offers a novel red emission quenching apart from normal concentration quenching in the glass system.No direct energy transfer but only little reabso rption occurs between Eu^(3+)and Ce^(3+)ions.The Ce^(3+)concentration effect is obvious on the electroluminescent color.The optimized color rendering index of 79.7,the CIE coordinates near natural white and the range of CCT from 3943 to 6097 K were obtained for the packaged white light emitting diodes(WLEDs)together with the excellent CCT stability higher than about 97.5%and the quadruple thermal conductivity than that of silicon resin.The work implies borophosphate glass based PiGs with fine transparence and energy conversion efficiency are promising for excellent WLEDs,while the LED by using the PiG sample without any yellow phosphor doped is of high color purity and has a potential use as the 465 nm blue source.展开更多
The preparation of high-efficiency phosphor is the key to the construction of white light-emitting diode(WLED)devices and their application in indoor photovoltaics.Compared with YVO_(4),InVO_(4)is not suitable as the ...The preparation of high-efficiency phosphor is the key to the construction of white light-emitting diode(WLED)devices and their application in indoor photovoltaics.Compared with YVO_(4),InVO_(4)is not suitable as the host material of lanthanide ions because of its strong self-luminescence.Here,the work focused on combining the broadband emission from InVO_(4)and the red luminescence from YVO_(4):Eu^(3+)to obtain enhanced and stable multicolor luminescence.The band structure,density of state,and optical properties were studied by density functional theory.The spectral configuration of YVO_(4):In^(3+)/Eu^(3+)with(112)surface appears to be broadening and redshifts with increasing layer number.When the In^(3+)concentration is 3.5 mol%,the YVO_(4):30%Eu^(3+)/In^(3+)emits the strongest light.The Judd-Ofelt parameterΩ2 of YVO_(4):In^(3+)/Eu^(3+)increases with increaing In^(3+)concentration,indicating that the symmetry decreases.By adjusting In^(3+)/Eu^(3+)contents,the YVO_(4):In^(3+)/Eu^(3+)not only can emit white light with a color rendering index of 95,but also can be used as high-efficiency red phosphor to build WLED devices with blue emitting N/Tb codoped carbon quantum dots(CQDs-N:Tb^(3+))and green emitting MOF:Tb^(3+)(MOF=metal organic framework),for which the color rendering index can also reach 95 and the color temperature is 5549 K.The manufactured WLED devices were further used to excite the silicon solar cell and make it show good photoelectric characteristics.展开更多
Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural ...Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural modification.The correlations among structural evolution,crystal-field environment,and luminescence properties were elucidated.Replacing Sr^(2+)with Gd^(3+)in(Sr,Gd)LiAl_(3)N_(4):Eu^(2+)leads to the enhanced crystal field splitting,larger Stokes shift,and increased structural polyhedron distortion differences,consequently resulting in spectral red-shift and broadening.For further spectral tuning,Mg,with lower electronegativity,was also introduced to modify the local crystal structure,consequently resulting in a further red-shift towards 675 nm and enhanced photoluminescence intensity in(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+).What’s more,w-LEDs were fabricated by using blue LED chip,blue,green,red and deep red((Sr,Gd)Li(Al,Mg)_(3)N_(4):Eu^(2+))phosphors whose color rendering index were Ra 96.0 and R997.7.All above results demonstrate that the partial replacements of Sr^(2+)by Gd^(3+)and Al^(3+)by Mg^(2+)are effective methods for spectral modulation and(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)phosphors are suitable for highquality full-spectrum WLEDs.展开更多
A series of single-composition emission-tunable CdWO4：Eu^3＋ uniform size nanorods were synthesized by polyvinylpyrrolidone（PVP） assisted hydrothermal process. The products were measured by powder X-ray diffraction...A series of single-composition emission-tunable CdWO4：Eu^3＋ uniform size nanorods were synthesized by polyvinylpyrrolidone（PVP） assisted hydrothermal process. The products were measured by powder X-ray diffraction（PXRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, photoluminescence, and fluorescent decay test. The results showed that reaction time, temperature, p H values and Eu^3＋ doped concentration played important roles in determining the morphologies and photoluminescent properties. And we also investigated its use in Ga N LED, warm-white-light could be obtained by the combination of the bright blue light originated from the charge transfer transition in the tungstate groups and the near UV light from LED chip with the red emission from 4f-4f transition of Eu^3＋, respectively. By properly tuning the doping concentration of Eu^3＋, chromaticity coordinates（0.30 0.22） could be achieved under the 380 nm excitation and its color rendering index was 80.6. So it has potential application in warm-WLED and replacing the commercial YAG：Ce phosphor which absence of red band emission.展开更多
To introduce ordered nano-structures inside a transparent amorphous matrix with superior optical and mechanical properties bears scientific and technological importance,yet limited success has been achieved.Here,via s...To introduce ordered nano-structures inside a transparent amorphous matrix with superior optical and mechanical properties bears scientific and technological importance,yet limited success has been achieved.Here,via simple melting-quenching and subsequent thermal activation,we report the successful preparation of transparent nano-structured glass-ceramics embedded in Sr2Lu F7 nano-crystals(~26 nm),as evidenced by X-ray diffraction,transmission electron microscopy(TEM),and high resolution TEM.The successful incorporation of dopants into formed Sr2Lu F7 nano-crystals with low phonon energy results in highly tunable blue–green photoemission,which depends on excitation wavelength,dopant type,and temperature.We found that Eu3+and Eu2+ions co-exist in this hybrid optical material,accompanied by the broadband blue emission of Eu2+and sharp red emissions of Eu3+.A series of optical characterizations are summoned,including emission/excitation spectrum and decay curve measurement,to reveal the reduction mechanism of Eu3+to Eu2+.Furthermore,near green–white photoemission is achieved via the enrichment of Tb3+/Eu3+into crystallized Sr2Lu F7 nano-crystals.The temperature-dependent visible photoemission reveals thermal activation energy increases with the precipitation of Sr2Lu F7 nano-crystals in a glass matrix,suggesting better thermal stability of glass-ceramics than precursor glasses.These results could not only deepen the understanding of glass-ceramics but also indicate the promising potential of Eu3+/Tb3+-ions-doped Sr2Lu F7 glass-ceramics for UV pumped white light emitting diodes(WLEDs)with good thermal stability.展开更多
We report a unique red light-emitting Eu-doped borosilicate glass to convert color for warm white light-emitting diodes. This glass can be excited from 394 nm-peaked near ultraviolet light, 466 nm-peaked blue light, t...We report a unique red light-emitting Eu-doped borosilicate glass to convert color for warm white light-emitting diodes. This glass can be excited from 394 nm-peaked near ultraviolet light, 466 nm-peaked blue light, to 534 nm- peaked green light to emit the desired red light with an excellent transmission in the wavelength range of 400-700 nm which makes this glass suitable for color conversion without a great cost of luminous power loss. In particular, when assembling this glass for commercial white light-emitting diodes, the tested results show that the color rendering index is improved to 84 with a loss of luminous power by 12 percent at average, making this variety of glass promising for inorganic ＂remote-phosphor＂ color conversion.展开更多
基金the CAS Priority Research program(XDB20010300,XDA21010204)National Natural Science Foundation of China(201501178)Natural Science Foundation of Fujian Province(2017H0048)。
文摘A series of YAG:Ce,Mn transparent ceramics were prepared via a solid-state reaction-vacuum sintering method.The effects of various Mn^2+–Si4+pair doping levels on the structure,transmittance,and luminescence properties were systematically investigated.These transparent ceramics have average grain sizes of 10–16μm,clean grain boundaries,and excellent transmittance up to 83.4%at 800 nm.Under the excitation of 460 nm,three obvious emission peaks appear at 533,590,and 745 nm,which can be assigned to the transition 5 d→4 f of Ce^3+and 4 T1→6 A1 of Mn^2+.Thus,the Mn^2+–Si4+pairs can effectively modulate the emission spectrum by compensating broad orange-red and red spectrum component to yield high quality warm white light.After the optimized YAG:Ce,Mn transparent ceramic packaged with blue light-emitting diode(LED)chips,correlated color temperature(CCT)as low as 3723 K and luminous efficiency(LE)as high as 96.54 lm/W were achieved,implying a very promising candidate for application in white light-emitting diodes(WLEDs)industry.
基金Project supported by the Joint Funds of the National Natural Science Foundation of China(U1932160)the National Natural Science Foundation of China(51605272)。
文摘Phosphor-in-glass(PiG)is a potential color convertor for high power WLEDs.A novel glass matrix with advanced performance is still a challenge.Recently,Eu^(3+)doped glass matrix has attracted much consideration mainly due to its red compensation.A new borophosphate matrix to realize Eu^(3+)red light was designed in the Na_(2)O-ZnO-P_(2)O_(5)-B_(2)O_(3)-Eu_(2)O_(3)system.Meanwhile,a series of PiGs composed of different concentrations of Y3Al5O12:Ce phosphor and the matrix were also fabricated by re-sintering.The crystallization of Eu^(3+)based phosphate offers a novel red emission quenching apart from normal concentration quenching in the glass system.No direct energy transfer but only little reabso rption occurs between Eu^(3+)and Ce^(3+)ions.The Ce^(3+)concentration effect is obvious on the electroluminescent color.The optimized color rendering index of 79.7,the CIE coordinates near natural white and the range of CCT from 3943 to 6097 K were obtained for the packaged white light emitting diodes(WLEDs)together with the excellent CCT stability higher than about 97.5%and the quadruple thermal conductivity than that of silicon resin.The work implies borophosphate glass based PiGs with fine transparence and energy conversion efficiency are promising for excellent WLEDs,while the LED by using the PiG sample without any yellow phosphor doped is of high color purity and has a potential use as the 465 nm blue source.
基金supported by the National Natural Science Foundation of China(No.22271080).
文摘The preparation of high-efficiency phosphor is the key to the construction of white light-emitting diode(WLED)devices and their application in indoor photovoltaics.Compared with YVO_(4),InVO_(4)is not suitable as the host material of lanthanide ions because of its strong self-luminescence.Here,the work focused on combining the broadband emission from InVO_(4)and the red luminescence from YVO_(4):Eu^(3+)to obtain enhanced and stable multicolor luminescence.The band structure,density of state,and optical properties were studied by density functional theory.The spectral configuration of YVO_(4):In^(3+)/Eu^(3+)with(112)surface appears to be broadening and redshifts with increasing layer number.When the In^(3+)concentration is 3.5 mol%,the YVO_(4):30%Eu^(3+)/In^(3+)emits the strongest light.The Judd-Ofelt parameterΩ2 of YVO_(4):In^(3+)/Eu^(3+)increases with increaing In^(3+)concentration,indicating that the symmetry decreases.By adjusting In^(3+)/Eu^(3+)contents,the YVO_(4):In^(3+)/Eu^(3+)not only can emit white light with a color rendering index of 95,but also can be used as high-efficiency red phosphor to build WLED devices with blue emitting N/Tb codoped carbon quantum dots(CQDs-N:Tb^(3+))and green emitting MOF:Tb^(3+)(MOF=metal organic framework),for which the color rendering index can also reach 95 and the color temperature is 5549 K.The manufactured WLED devices were further used to excite the silicon solar cell and make it show good photoelectric characteristics.
基金supported by the National Key Research and Development Program of China(2021YFB3500402)。
文摘Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural modification.The correlations among structural evolution,crystal-field environment,and luminescence properties were elucidated.Replacing Sr^(2+)with Gd^(3+)in(Sr,Gd)LiAl_(3)N_(4):Eu^(2+)leads to the enhanced crystal field splitting,larger Stokes shift,and increased structural polyhedron distortion differences,consequently resulting in spectral red-shift and broadening.For further spectral tuning,Mg,with lower electronegativity,was also introduced to modify the local crystal structure,consequently resulting in a further red-shift towards 675 nm and enhanced photoluminescence intensity in(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+).What’s more,w-LEDs were fabricated by using blue LED chip,blue,green,red and deep red((Sr,Gd)Li(Al,Mg)_(3)N_(4):Eu^(2+))phosphors whose color rendering index were Ra 96.0 and R997.7.All above results demonstrate that the partial replacements of Sr^(2+)by Gd^(3+)and Al^(3+)by Mg^(2+)are effective methods for spectral modulation and(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)phosphors are suitable for highquality full-spectrum WLEDs.
基金Project supported by the National Natural Science Foundation of China(21301115)the Shanghai University Innovation Fund(sdcx2012005)Funding Scheme for Training Young Teachers in Colleges and Universities(ZZSD12025)
文摘A series of single-composition emission-tunable CdWO4：Eu^3＋ uniform size nanorods were synthesized by polyvinylpyrrolidone（PVP） assisted hydrothermal process. The products were measured by powder X-ray diffraction（PXRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, photoluminescence, and fluorescent decay test. The results showed that reaction time, temperature, p H values and Eu^3＋ doped concentration played important roles in determining the morphologies and photoluminescent properties. And we also investigated its use in Ga N LED, warm-white-light could be obtained by the combination of the bright blue light originated from the charge transfer transition in the tungstate groups and the near UV light from LED chip with the red emission from 4f-4f transition of Eu^3＋, respectively. By properly tuning the doping concentration of Eu^3＋, chromaticity coordinates（0.30 0.22） could be achieved under the 380 nm excitation and its color rendering index was 80.6. So it has potential application in warm-WLED and replacing the commercial YAG：Ce phosphor which absence of red band emission.
基金the National Natural Science Foundation of China(Nos.51902178,11804188,51702172,and 51802285)the Natural Science Foundation of Shandong Province(No.ZR201807060932)the Open Fund of the State Key Laboratory of Luminescent Materials and Devices(South China University of Technology)(No.2019-skllmd-15)。
文摘To introduce ordered nano-structures inside a transparent amorphous matrix with superior optical and mechanical properties bears scientific and technological importance,yet limited success has been achieved.Here,via simple melting-quenching and subsequent thermal activation,we report the successful preparation of transparent nano-structured glass-ceramics embedded in Sr2Lu F7 nano-crystals(~26 nm),as evidenced by X-ray diffraction,transmission electron microscopy(TEM),and high resolution TEM.The successful incorporation of dopants into formed Sr2Lu F7 nano-crystals with low phonon energy results in highly tunable blue–green photoemission,which depends on excitation wavelength,dopant type,and temperature.We found that Eu3+and Eu2+ions co-exist in this hybrid optical material,accompanied by the broadband blue emission of Eu2+and sharp red emissions of Eu3+.A series of optical characterizations are summoned,including emission/excitation spectrum and decay curve measurement,to reveal the reduction mechanism of Eu3+to Eu2+.Furthermore,near green–white photoemission is achieved via the enrichment of Tb3+/Eu3+into crystallized Sr2Lu F7 nano-crystals.The temperature-dependent visible photoemission reveals thermal activation energy increases with the precipitation of Sr2Lu F7 nano-crystals in a glass matrix,suggesting better thermal stability of glass-ceramics than precursor glasses.These results could not only deepen the understanding of glass-ceramics but also indicate the promising potential of Eu3+/Tb3+-ions-doped Sr2Lu F7 glass-ceramics for UV pumped white light emitting diodes(WLEDs)with good thermal stability.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50872091 and 21076161)the Tianjin Municipal Sci/Tech. Commission, China (Grant Nos. 10SYSYJC28100 and 2006ZD30)the Tianjin Municipal Higher Education Commission, China (Grant No. 20110304)
文摘We report a unique red light-emitting Eu-doped borosilicate glass to convert color for warm white light-emitting diodes. This glass can be excited from 394 nm-peaked near ultraviolet light, 466 nm-peaked blue light, to 534 nm- peaked green light to emit the desired red light with an excellent transmission in the wavelength range of 400-700 nm which makes this glass suitable for color conversion without a great cost of luminous power loss. In particular, when assembling this glass for commercial white light-emitting diodes, the tested results show that the color rendering index is improved to 84 with a loss of luminous power by 12 percent at average, making this variety of glass promising for inorganic ＂remote-phosphor＂ color conversion.
