Nowadays,high-quality phosphor-converted white light-emitting diodes(pc-WLEDs)ought to include cyan-emitting phosphors allowing for full-spectrum light similar to sunlight.Herein,we report a garnetstructured Ce^(3+)-d...Nowadays,high-quality phosphor-converted white light-emitting diodes(pc-WLEDs)ought to include cyan-emitting phosphors allowing for full-spectrum light similar to sunlight.Herein,we report a garnetstructured Ce^(3+)-doped SrLu_(2)Ga_(1.5)Al_(2.5)SiO_(12)(SLGASO)phosphor that significantly compensates for the absence of cyan light,known as the"cyan cavity".The SLGASO host crystallizes into a cubic structure with the Ia3d space group.The cell parameters were determined using Rietveld refinement.Under430 nm blue excitation,SLGASO:Ce^(3+)emits intense cyan-green light in the 450-700 nm wavelength range.The representative SLGASO:0.07Ce^(3+)phosphor has an internal quantum efficiency(IQE)of 95.4%and excellent thermal stability,remaining 92.7%of its initial emission intensity at 152℃.After 155 d of immersion in water,the luminous intensity of SLGASO:0.07Ce^(3+)remains constant,confirming its waterproofness.Furthermore,a pc-WLED device with luminous efficiency(LE)of 101.58 lm/W,color rendering index(Ra)of 91,correlated color temperature(CCT)of 4536 K,and Commission Internationale de L'Eclairage(CIE)chromaticity coordinates of(0.3555,0.3390)was fabricated by combining asprepared cyan-green-emitting SLGASO:0.07Ce^(3+),yellow-emitting Y_(3)Al_(5)O_(12):Ce^(3+)(YAG:Ce^(3+)),and redemitting(Ca,Sr)AlSiN_(3):Eu^(2+)phosphors,as well as a 450 nm blue chip.These findings indicate that SLGASO:0.07Ce^(3+)phosphor can bridge the cyan gap and improve the performance of as-fabricated fullvisible-spectrum WLEDs.展开更多
Er^(3+)-doped BaLaGaO_(4)green phosphors was synthesized through a high-temperature solid-state reaction technique.The phase structure and morphology test results of the phosphor indicate that the BaLaGaO_(4)material ...Er^(3+)-doped BaLaGaO_(4)green phosphors was synthesized through a high-temperature solid-state reaction technique.The phase structure and morphology test results of the phosphor indicate that the BaLaGaO_(4)material was successfully synthesized and Er^(3+)ions were successfully doped into the main lattice.This doping does change the basic structure of the crystal.BaLaGaO_(4):Er^(3+)phosphor exhibits bright green emission centered at 545 nm when excited by 381 nm ultraviolet light or 980 nm near-infrared light.The optimal doping concentration is found to be x=0.04.To quantify the temperature sensitivity of the phosphor,the fluorescence intensity ratio method was used.Within the temperature range of 298-473 K,the maximum relative sensitivities are 1.35%/K(298 K,381 nm)and 1.45%/K(298 K,980 nm),respectively.The maximum absolute sensitivities are 0.67%/K(473 K,381 nm)and 0.69%/K(473 K,980 nm),respectively.Finally,white light-emitting diodes(WLEDs)with a high colour index of Ra=82and a relatively low correlated colour temperature of CCT=5064 K are obtained by integrating the synthesized BaLaGaO_(4):0.04Er^(3+)green phosphor into warm WLEDs devices.These results suggest that Er^(3+)-activated BaLaGaO_(4)multifunctional phosphors hold considerable promise in the areas of optical temperature sensing and WLEDs phosphor conversion.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
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
Inorganic lead-free double perovskites have the advantages of low toxicity,broadband emission,and good stability,which make them promising luminescent materials for lighting applications.However,due to the limited reg...Inorganic lead-free double perovskites have the advantages of low toxicity,broadband emission,and good stability,which make them promising luminescent materials for lighting applications.However,due to the limited regulation of their self-trapped exciton emission,it is still greatly challenging to achieve white light emitting from a single double perovskite host.Herein,efficient and tunable white light is realized in Cs_(2)NalnCl_(6)∶Sb^(3+),Tb^(3+),Sm^(3+)double perovskite by controlling the ratios of the doped three ions with blue,green,and red emissions,respectively.The steady-state and transient fluorescence spectra of singly-and doubly-doped double perovskites reveal the existence of multiple energy transfer channels in the triply-doped phosphors,including from Sb^(3+)to Tb^(3+),Sb^(3+)to Sm^(3+),and Tb^(3+)to Sm^(3+).Benefiting from these channels,the color coordinates of the triply-doped phosphors can cross the whole white light area of the CIE chromaticity diagram by adjusting the ratios of the three dopants,and the maximum internal quantum yield of the white light phosphors is 66.61%.The white emission phosphors show the characteristic of being independent of excitation wavelength within 310-360 nm.Furthermore,the emission intensity at 430 K of the white light phosphor Cs_(2)NalnCl_(6)∶0.01Sb^(3+),0.65Tb^(3+),0.20Sm^(3+)remains 50% of that at room temperature.A WLED device fabricated with the phosphor and a 365 nm LED chip exhibits a high color rendering index of 90.9,correlated color temperature of 5469 K,and CIE coordinates of(0.333 and 0.328).The results indicate that the as-prepared double perovskite materials are promising candidates in the solid-state lighting field.展开更多
Definite emission colorfrom rare-earth Eu^(2+)cannot be guaranteed in distinct hosts because its spectrum behavior is strongly dependent on surrounding microenvironment.Herein,we propose a strategy of heterostructure ...Definite emission colorfrom rare-earth Eu^(2+)cannot be guaranteed in distinct hosts because its spectrum behavior is strongly dependent on surrounding microenvironment.Herein,we propose a strategy of heterostructure polyhedron BO3-PO4 substitution that can realize customizable and even predictable Eu^(2+)emission.Taking Sr_(3)La(PO_(4))_(3):Eu^(2+)blue phosphor as host,we prepared a series of BO3-PO4 substitution-designed Sr_(3)La(PO_(4))_(3):Eu^(2+)(SLP_(3-x)B_(x):Eu^(2+))phosphors via solid-state reaction.Structural and spectral analyses demonstrate that substitution of PO_(4)with BO_(3)unit drives Eu^(2+)to migrate from original occupied Sr sites to unoccupied six-coordinated La sites,bringing out a brand-new broadband yellow-emitting peak at 530 nm,enabling an efficient spectrum tailoring from initial blue emission at 420 nm to white-light and then yellow.Strikingly,we find that the resultant Eu^(2+)spectrum behavior in as-prepared SLP_(3-x)B_(x):Eu^(2+)and Eu^(2+)-doped other borophosphate phosphors is highly similar(although they have different microenvironments).Such exciting findings indicate that proposed BO3-PO4 substitution-strategy possesses an ability of predicting emission by modulating Eu^(2+)site-selective occupation.Utilizing SLP_(3-x)B_(x):Eu^(2+)(x=0.1 and 0.4)phosphors,we fabricated optical temperature sensor and white LED prototypes,showcasing remarkable temperature sensitivity of S_(r)=1.1%/K and good color rendering index(CRI)of 83.This work may aid the discovery of novel functional materials with specific,desirablephysicochemical properties.展开更多
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
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
Nano phosphors of 2%Dy^(3+)(wt%)doped La_(2)MgTiO_(6) and monovalent/divalent/trivalent co-doped La_(1.98)Dy_(0.02)MgTiO_(6):x%A^(y+)(A^(y+):Li+,Ba^(2+),Sr^(2+),Bi^(3+),and Sm^(3+);0≤x≤2 wt%)were synthesized by comb...Nano phosphors of 2%Dy^(3+)(wt%)doped La_(2)MgTiO_(6) and monovalent/divalent/trivalent co-doped La_(1.98)Dy_(0.02)MgTiO_(6):x%A^(y+)(A^(y+):Li+,Ba^(2+),Sr^(2+),Bi^(3+),and Sm^(3+);0≤x≤2 wt%)were synthesized by combustion method.From the XRD data,it is deduced that an increase in the valency of co-dopant increases the crystallinity of the double perovskite orthorhombic nanocrystal structure.With an increase in co-dopant size,an elevation in optical bandgap is visible with the highest bandgap of 3.835 eV for Bi^(3+).The photo-absorption is monotonically broadened for Sr^(2+),Sm^(3+),and Li+around 200-450 nm.Under351 nm,Dy^(3+)triggered lattice shows major characteristic emission peaks at 480 nm(^(4)F_(9/2)→^(6)H_(15/2)),574 nm(^(4)F_(9/2)→^(6)H_(13/2)),and 670 nm(^(4)F_(9/2)→^(6)H_(11/2)).leading to near white light emission with CIE coordinates(0.341,0.376).Upon co-doping,the PL intensity is significantly increased with maximum emission for trivalent Sm^(3+),followed by divalent Sr^(2+)and monovalent Li+respectively.With increasing excitation wavelength,Sr^(2+)shows a dominated output and it is found that divalent Sr^(2+)is a potential codopant that could enhance luminescence intensity up to 6 times with a Sr^(2+)→Dy^(3+)energy transfer efficiency of 86%.It is specified that the CIE coordinates of Li+co-doped samples show ideal white emission with color coordinates(0.333,0.336).The concluding outcomes signify the noblest rare earth Sm^(3+)co-doping and thus Sm^(3+)→Dy^(3+)energy transfer mechanism is discussed in detail.展开更多
Stability hinders further development of all-inorganic CsPb X_(3)(X=Cl,Br,I)quantum dots(QDs)although they exhibit promising prospects in optoelectronic applications.Coating perovskite quantum dots(PQDs)with a glass n...Stability hinders further development of all-inorganic CsPb X_(3)(X=Cl,Br,I)quantum dots(QDs)although they exhibit promising prospects in optoelectronic applications.Coating perovskite quantum dots(PQDs)with a glass network to form QD glass can significantly improve their stability.However,the dense glass network degrades their luminescent performance.In this work,the crystallization behavior of PQDs in glass and better luminescence properties are prompted by introducing titanium dioxide into borosilicate glass.The luminescence intensity of TiO_(2)-doped CsPbBr_(3)QD glass is increased by 1.6 times and the PLQY is increased from 49.8%to 79%compared to the undoped glass.Evidence proves that the improved prop-erties are attributed to the enhanced nucleation effect of titanium dioxide during the annealing process.Benefiting from the densification of the glass network caused by titanium dioxide doping,the stability of the PQD glass is further improved.LED devices with an ultra-wide color gamut that fully covers the NTSC1953 standard and achieves 128.6%of the NTSC1953 standard as well as 91.1%of the Rec.2020 stan-dard were fabricated by coupling PQD glass powder,demonstrating promising commercial applications of PQD glass in optoelectronic displays.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
Highly pure red phosphors LiM(PO_(3))_(3):Eu^(3+)(M=Sr,Ca) doped with Eu^(3+)(1 mol%) were synthesized via solution combustion method and their crystal structure and luminescence dynamics were studied to explore its s...Highly pure red phosphors LiM(PO_(3))_(3):Eu^(3+)(M=Sr,Ca) doped with Eu^(3+)(1 mol%) were synthesized via solution combustion method and their crystal structure and luminescence dynamics were studied to explore its suitability in white light emitting diodes.The Rietveld refinement analysis of the powder Xray diffraction patterns reveals that the phosphors belong to the pure triclinic phase of LiSr(PO_(3))_(3) and LiCa(PO_(3)) with space group P-1(2).The scanning electron microscopy images showed the agglomerated morphology.The photoluminescence emission spectra under 393 nm show an orange band at 594 nm and a red band at 613 nm ascribed to ^(5)D_(0)→^(7)F_(1).^(5)D_(0)→^(7)F_(2) transitions of Eu^(3+)ion in both the phosphors.Moreover,the spectroscopic properties such as luminescence behaviour,and Stark splitting were used to examine the symmetry of Eu^(3+)ions in LiM(PO_(3))_(3):Es^(3+)(M=Sr,Ca) phosphors in terms of distortion induced upon doping.The Stark splitting shows that the actual site symmetry for Eu^(3+)ion was estimated to be D_(2) type for both phosphors.The photometric properties of LiCa(PO_(3))_(3):Eu^(3+)such as Commission International de l'Eclairage coordinates(x=0.64,y=0.36) near to the standard one(red),high color purity(95%) and higher brightness reveal that the phosphor has the capability of acting as a red component in n-UV white light emitting diodes.展开更多
基金supported by the National Natural Science Foundations of China(21801254,52002411,52272174,22205017,U1301242)China Postdoctoral Science Foundation(2022M720400,2023M743978)+1 种基金Specialized Research Fund for the Doctoral Program of Higher Education of China(20130171130001)the Ministry of Science,Technological Development,and Innovation of the Republic of Serbia(451-03-66/2024-03/200017)。
文摘Nowadays,high-quality phosphor-converted white light-emitting diodes(pc-WLEDs)ought to include cyan-emitting phosphors allowing for full-spectrum light similar to sunlight.Herein,we report a garnetstructured Ce^(3+)-doped SrLu_(2)Ga_(1.5)Al_(2.5)SiO_(12)(SLGASO)phosphor that significantly compensates for the absence of cyan light,known as the"cyan cavity".The SLGASO host crystallizes into a cubic structure with the Ia3d space group.The cell parameters were determined using Rietveld refinement.Under430 nm blue excitation,SLGASO:Ce^(3+)emits intense cyan-green light in the 450-700 nm wavelength range.The representative SLGASO:0.07Ce^(3+)phosphor has an internal quantum efficiency(IQE)of 95.4%and excellent thermal stability,remaining 92.7%of its initial emission intensity at 152℃.After 155 d of immersion in water,the luminous intensity of SLGASO:0.07Ce^(3+)remains constant,confirming its waterproofness.Furthermore,a pc-WLED device with luminous efficiency(LE)of 101.58 lm/W,color rendering index(Ra)of 91,correlated color temperature(CCT)of 4536 K,and Commission Internationale de L'Eclairage(CIE)chromaticity coordinates of(0.3555,0.3390)was fabricated by combining asprepared cyan-green-emitting SLGASO:0.07Ce^(3+),yellow-emitting Y_(3)Al_(5)O_(12):Ce^(3+)(YAG:Ce^(3+)),and redemitting(Ca,Sr)AlSiN_(3):Eu^(2+)phosphors,as well as a 450 nm blue chip.These findings indicate that SLGASO:0.07Ce^(3+)phosphor can bridge the cyan gap and improve the performance of as-fabricated fullvisible-spectrum WLEDs.
基金supported by the National Natural Science Foundation of China(52403403)Guizhou Provincial Basic Research Program(Natural Science)(Qian ke he ji chu-ZK2024 YiBan 095)。
文摘Er^(3+)-doped BaLaGaO_(4)green phosphors was synthesized through a high-temperature solid-state reaction technique.The phase structure and morphology test results of the phosphor indicate that the BaLaGaO_(4)material was successfully synthesized and Er^(3+)ions were successfully doped into the main lattice.This doping does change the basic structure of the crystal.BaLaGaO_(4):Er^(3+)phosphor exhibits bright green emission centered at 545 nm when excited by 381 nm ultraviolet light or 980 nm near-infrared light.The optimal doping concentration is found to be x=0.04.To quantify the temperature sensitivity of the phosphor,the fluorescence intensity ratio method was used.Within the temperature range of 298-473 K,the maximum relative sensitivities are 1.35%/K(298 K,381 nm)and 1.45%/K(298 K,980 nm),respectively.The maximum absolute sensitivities are 0.67%/K(473 K,381 nm)and 0.69%/K(473 K,980 nm),respectively.Finally,white light-emitting diodes(WLEDs)with a high colour index of Ra=82and a relatively low correlated colour temperature of CCT=5064 K are obtained by integrating the synthesized BaLaGaO_(4):0.04Er^(3+)green phosphor into warm WLEDs devices.These results suggest that Er^(3+)-activated BaLaGaO_(4)multifunctional phosphors hold considerable promise in the areas of optical temperature sensing and WLEDs phosphor conversion.
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 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supported by grants from the National Natural Science Foundation of China(NSFC Nos.51972347 and 21771195).
文摘Inorganic lead-free double perovskites have the advantages of low toxicity,broadband emission,and good stability,which make them promising luminescent materials for lighting applications.However,due to the limited regulation of their self-trapped exciton emission,it is still greatly challenging to achieve white light emitting from a single double perovskite host.Herein,efficient and tunable white light is realized in Cs_(2)NalnCl_(6)∶Sb^(3+),Tb^(3+),Sm^(3+)double perovskite by controlling the ratios of the doped three ions with blue,green,and red emissions,respectively.The steady-state and transient fluorescence spectra of singly-and doubly-doped double perovskites reveal the existence of multiple energy transfer channels in the triply-doped phosphors,including from Sb^(3+)to Tb^(3+),Sb^(3+)to Sm^(3+),and Tb^(3+)to Sm^(3+).Benefiting from these channels,the color coordinates of the triply-doped phosphors can cross the whole white light area of the CIE chromaticity diagram by adjusting the ratios of the three dopants,and the maximum internal quantum yield of the white light phosphors is 66.61%.The white emission phosphors show the characteristic of being independent of excitation wavelength within 310-360 nm.Furthermore,the emission intensity at 430 K of the white light phosphor Cs_(2)NalnCl_(6)∶0.01Sb^(3+),0.65Tb^(3+),0.20Sm^(3+)remains 50% of that at room temperature.A WLED device fabricated with the phosphor and a 365 nm LED chip exhibits a high color rendering index of 90.9,correlated color temperature of 5469 K,and CIE coordinates of(0.333 and 0.328).The results indicate that the as-prepared double perovskite materials are promising candidates in the solid-state lighting field.
基金the Natural Science Foundation of Xinjiang Uygur Autonomous Region(2021D01E19,2022TSYCXC0016)the Project of youth science and technology innovation talent project of Xinjiang Normal University(XJNUQB2022-15)+1 种基金the National Natural Science Foundations of China(52262029,51762040)Postgraduate Research and the Research Fund of Xinjiang Normal University Research Platform Student Project(XSY202201013).
文摘Definite emission colorfrom rare-earth Eu^(2+)cannot be guaranteed in distinct hosts because its spectrum behavior is strongly dependent on surrounding microenvironment.Herein,we propose a strategy of heterostructure polyhedron BO3-PO4 substitution that can realize customizable and even predictable Eu^(2+)emission.Taking Sr_(3)La(PO_(4))_(3):Eu^(2+)blue phosphor as host,we prepared a series of BO3-PO4 substitution-designed Sr_(3)La(PO_(4))_(3):Eu^(2+)(SLP_(3-x)B_(x):Eu^(2+))phosphors via solid-state reaction.Structural and spectral analyses demonstrate that substitution of PO_(4)with BO_(3)unit drives Eu^(2+)to migrate from original occupied Sr sites to unoccupied six-coordinated La sites,bringing out a brand-new broadband yellow-emitting peak at 530 nm,enabling an efficient spectrum tailoring from initial blue emission at 420 nm to white-light and then yellow.Strikingly,we find that the resultant Eu^(2+)spectrum behavior in as-prepared SLP_(3-x)B_(x):Eu^(2+)and Eu^(2+)-doped other borophosphate phosphors is highly similar(although they have different microenvironments).Such exciting findings indicate that proposed BO3-PO4 substitution-strategy possesses an ability of predicting emission by modulating Eu^(2+)site-selective occupation.Utilizing SLP_(3-x)B_(x):Eu^(2+)(x=0.1 and 0.4)phosphors,we fabricated optical temperature sensor and white LED prototypes,showcasing remarkable temperature sensitivity of S_(r)=1.1%/K and good color rendering index(CRI)of 83.This work may aid the discovery of novel functional materials with specific,desirablephysicochemical properties.
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.
文摘Nano phosphors of 2%Dy^(3+)(wt%)doped La_(2)MgTiO_(6) and monovalent/divalent/trivalent co-doped La_(1.98)Dy_(0.02)MgTiO_(6):x%A^(y+)(A^(y+):Li+,Ba^(2+),Sr^(2+),Bi^(3+),and Sm^(3+);0≤x≤2 wt%)were synthesized by combustion method.From the XRD data,it is deduced that an increase in the valency of co-dopant increases the crystallinity of the double perovskite orthorhombic nanocrystal structure.With an increase in co-dopant size,an elevation in optical bandgap is visible with the highest bandgap of 3.835 eV for Bi^(3+).The photo-absorption is monotonically broadened for Sr^(2+),Sm^(3+),and Li+around 200-450 nm.Under351 nm,Dy^(3+)triggered lattice shows major characteristic emission peaks at 480 nm(^(4)F_(9/2)→^(6)H_(15/2)),574 nm(^(4)F_(9/2)→^(6)H_(13/2)),and 670 nm(^(4)F_(9/2)→^(6)H_(11/2)).leading to near white light emission with CIE coordinates(0.341,0.376).Upon co-doping,the PL intensity is significantly increased with maximum emission for trivalent Sm^(3+),followed by divalent Sr^(2+)and monovalent Li+respectively.With increasing excitation wavelength,Sr^(2+)shows a dominated output and it is found that divalent Sr^(2+)is a potential codopant that could enhance luminescence intensity up to 6 times with a Sr^(2+)→Dy^(3+)energy transfer efficiency of 86%.It is specified that the CIE coordinates of Li+co-doped samples show ideal white emission with color coordinates(0.333,0.336).The concluding outcomes signify the noblest rare earth Sm^(3+)co-doping and thus Sm^(3+)→Dy^(3+)energy transfer mechanism is discussed in detail.
基金sponsored by the Hengdian Group Holding Co.LTDsupported by the joint fund from Hengdian Group and Shanghai Institute of Ceram-ics,Chinese Academy of Sciences
文摘Stability hinders further development of all-inorganic CsPb X_(3)(X=Cl,Br,I)quantum dots(QDs)although they exhibit promising prospects in optoelectronic applications.Coating perovskite quantum dots(PQDs)with a glass network to form QD glass can significantly improve their stability.However,the dense glass network degrades their luminescent performance.In this work,the crystallization behavior of PQDs in glass and better luminescence properties are prompted by introducing titanium dioxide into borosilicate glass.The luminescence intensity of TiO_(2)-doped CsPbBr_(3)QD glass is increased by 1.6 times and the PLQY is increased from 49.8%to 79%compared to the undoped glass.Evidence proves that the improved prop-erties are attributed to the enhanced nucleation effect of titanium dioxide during the annealing process.Benefiting from the densification of the glass network caused by titanium dioxide doping,the stability of the PQD glass is further improved.LED devices with an ultra-wide color gamut that fully covers the NTSC1953 standard and achieves 128.6%of the NTSC1953 standard as well as 91.1%of the Rec.2020 stan-dard were fabricated by coupling PQD glass powder,demonstrating promising commercial applications of PQD glass in optoelectronic displays.
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Defence Research and Development Organization (DRDO),Govt.of India for financial support under DIA -KCOE (Kalam Centre of Excellence) reference no.KCST-SS02/2020。
文摘Highly pure red phosphors LiM(PO_(3))_(3):Eu^(3+)(M=Sr,Ca) doped with Eu^(3+)(1 mol%) were synthesized via solution combustion method and their crystal structure and luminescence dynamics were studied to explore its suitability in white light emitting diodes.The Rietveld refinement analysis of the powder Xray diffraction patterns reveals that the phosphors belong to the pure triclinic phase of LiSr(PO_(3))_(3) and LiCa(PO_(3)) with space group P-1(2).The scanning electron microscopy images showed the agglomerated morphology.The photoluminescence emission spectra under 393 nm show an orange band at 594 nm and a red band at 613 nm ascribed to ^(5)D_(0)→^(7)F_(1).^(5)D_(0)→^(7)F_(2) transitions of Eu^(3+)ion in both the phosphors.Moreover,the spectroscopic properties such as luminescence behaviour,and Stark splitting were used to examine the symmetry of Eu^(3+)ions in LiM(PO_(3))_(3):Es^(3+)(M=Sr,Ca) phosphors in terms of distortion induced upon doping.The Stark splitting shows that the actual site symmetry for Eu^(3+)ion was estimated to be D_(2) type for both phosphors.The photometric properties of LiCa(PO_(3))_(3):Eu^(3+)such as Commission International de l'Eclairage coordinates(x=0.64,y=0.36) near to the standard one(red),high color purity(95%) and higher brightness reveal that the phosphor has the capability of acting as a red component in n-UV white light emitting diodes.
