Sol-gel method was utilized to synthesize two different series of red silicate phosphors:MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3:Eu2+, Dy3+, ...Sol-gel method was utilized to synthesize two different series of red silicate phosphors:MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3:Eu2+, Dy3+, Mn2+. TGA curves of the gel precursor for two series depicted that the loss of residual organic groups and NO3 groups occurs below 450 ℃. According to the XRD patterns, the major diffraction peaks of the MgSiO3 and Mg2SiO4 series are consistent with a proto-enstatite structure (JCPDS No.11-0273) and a forsterite structure (JCPDS No.85-1364) respectively. With the excitation at 415 nm, the red emission band of Mn2+ ions is peaked at 661 nm for MgSiO3:1%(atom fraction) Mn2+ or 644 nm for Mg2SiO4:1%(atom fraction) Mn2+. Compared with Mg2SiO4:Mn2+ samples, MgSiO3:Mn2+ samples exhibit higher luminescence intensity and higher quenching concentration. In addition, the two series co-doped with Eu2+, Dy3+, Mn2+ were also prepared. Photo-luminescence and afterglow properties of the two co-doped series were analyzed, which show that MgSiO3:Eu2+, Dy3+, Mn2+ is more suitable for a red long-lasting phosphor.展开更多
A type of red luminescent Sr3Al2O6:Eu2+, Dy3+ phosphor powder is synthesised by sol-gel-combustion processing, with metal nitrates used as the source of metal ions and citric acid as a chelating agent of metal ions...A type of red luminescent Sr3Al2O6:Eu2+, Dy3+ phosphor powder is synthesised by sol-gel-combustion processing, with metal nitrates used as the source of metal ions and citric acid as a chelating agent of metal ions. By tracing the formation process of the sol-gel, it is found that it is necessary to reduce the amount of NO3 by dropping ethanol into the solution for forming a stable and homogeneous sol-gel. Thermogravimetric and Differential Scanning Calorimeter Analysis, x-ray diffractionmeter, scanning electron microscopy and photoluminescence spectroscopy are used to investigate the luminescent properties of the as-synthesised Sr3A1206:Eu2+, Dy3+. The results reveal that the Sr3Al2O6 crystallises completely when the combustion ash is sintered at 1250℃. The excitation and the emission spectra indicate that the excitation broadband lies mainly in a visible range and the phosphors emit a strong light at 618 nm under the excitation of 472 nm. The afterglow of (Sr0.94Eu0.03Dy0.03)3Al2O6 phosphors sintered at 1250℃ lasts for over 1000 s when the excited source is cut off.展开更多
A series of(Y_(1-y), Gdy)_(0.95-x)(P_y, V_(1-y))O_4 :0.05Eu^(3+), xBi^(3+)+phosphors have been successfully prepared by a subsection method. The crystal structure, surface morphology and luminescence properties were i...A series of(Y_(1-y), Gdy)_(0.95-x)(P_y, V_(1-y))O_4 :0.05Eu^(3+), xBi^(3+)+phosphors have been successfully prepared by a subsection method. The crystal structure, surface morphology and luminescence properties were investigated. It was found that the sintered samples crystallized in a tetragonal crystal system with space group I_(41)/amd(a = b = 0.7119 nm, c = 0.6290 nm). The products presented rod-like morphology with length of 100-150 nm and width of 50-100 nm. A maximum peak at 619 nm(~5D_0 →~7F_2) was observed in emission spectrum of the phosphors. It was also found that co-doping of Bi^(3+)+, P5+and Gd^(3+)ions into YVO_4:Eu^(3+)can not only made the right edge of the excitation band shift to the long-wavelength region, but also increased the emission intensity at 619 nm sharply and decreased the lifetime of fluorescence decay. These results may expand the application scope of the phosphors.展开更多
A series of (SrNa)2-xEux(MoO4)3 red phosphors have been synthesized by using the sol-gel method. X-ray diffraction, used to characterize the crystallization process of the phosphor precursors, indicates that the (SrNa...A series of (SrNa)2-xEux(MoO4)3 red phosphors have been synthesized by using the sol-gel method. X-ray diffraction, used to characterize the crystallization process of the phosphor precursors, indicates that the (SrNa)2-xEux(MoO4)3 phosphors had an SrMoO4 structure. The properties of these resulting phosphors have also been characterized by using photoluminescence (PL) spectra. The PL results indicate that all of the (SrNa)2-xEux(MoO4)3 phosphors exhibit intense red emissions under 275, 395, and 465-nm excitation. The two strongest lines at 395 and 465 nm in the excitation spectra of these phosphors match well with the two popular emissions from near-UV and blue GaN-based light-emitting diodes. Some process parameters for Eu3+ concentration, (C6H8O7)·H2O concentration, and solution pH value were also investigated. For (SrNa)2-xEux(MoO4)3 phosphors, there are two maximum emission intensities appearing with x = 0.6 and x = 1.4, respectively. When the molar ratio of citric acid is equal to that of metal cations and the solution pH is almost 4, (SrNa)2-xEux(MoO4)3 shows the strongest emission intensity compared to those under other conditions.展开更多
The luminescent properties of Eu^3+doped Ca2SiO4 red phosphors synthesized by the flux fusion reaction method were investigated. It was found that the excitation spectrum included two regions: the weak excitation ba...The luminescent properties of Eu^3+doped Ca2SiO4 red phosphors synthesized by the flux fusion reaction method were investigated. It was found that the excitation spectrum included two regions: the weak excitation band below 325 nm and strong narrow peaks above 325 nm. The main peak of the excitation band was located at 400 nm. The peaks located at 290 nm were assigned to the combination of the charge transfer transition of O-Eu, peaks above 325 nm (325, 385, 400, 470, 511, and 539 nm) were assigned to the f-f transitions of Eu^3+. The emission spectrum was dominated by the red peak located at 612 nm due to the electric dipole transition of ^5D0-^7F2. In addition, the effects of the Eu^3+ content and charge compensators of Li^+, Na^+, K^+, and Cl^- ions on the emission intensity were investigated. The experiment results suggested that the strongest emission was obtained when the concentration of the Eu^3+ ions was 0.3 mol^-1, and Li^+ ions gave the best improvement to enhance the emission intensity. Ca2SiO4:Eu^3+, Li^+ was thus suitable for low-cost trichromatic white light emitting diodes (WLED) based on UV InGaN chip.展开更多
Red phosphor (Y, Gd)BO3:Eu3+ with grain shape, small size, non-agglomerate, high crystallinity and good photoluminescence (PL) intensity was prepared by a complex method that the precursor of the phosphor was prepared...Red phosphor (Y, Gd)BO3:Eu3+ with grain shape, small size, non-agglomerate, high crystallinity and good photoluminescence (PL) intensity was prepared by a complex method that the precursor of the phosphor was prepared by co-precipitation method and the phosphor was prepared by combustion method. The SEM photos and the photoluminescence spectrum excited under VUV show that the morphology and luminescent properties of this phosphor are satisfied when an appropriate amount of urea was adopted as the combustion agent in the preparation procedure.展开更多
Ca(NO3)2·4H2O, Eu(NO3)3 and H2C2O4·2H2O were adopted to synthesize CaO: Eu3+ with the chemical co-precipitation method, and the effects of the calcination temperature and Eu3+ doping concentration on ...Ca(NO3)2·4H2O, Eu(NO3)3 and H2C2O4·2H2O were adopted to synthesize CaO: Eu3+ with the chemical co-precipitation method, and the effects of the calcination temperature and Eu3+ doping concentration on the phosphor structure and its luminescent properties were investigated by TG-SDTA, XRD, and PL-PLE. The results confirm that the Eu3+ ions as luminescent centers substi-tutes Ca2+ sites without changing the crystal structure of cubic CaO. The optimum calcination tem-perature and the optimum concentration of Eu3+ are 1 100 ℃ and 1 mol%, respectively, under which the best crystallinity and highest PL intensity appeared. The maximum emission wavelength is 592 nm (5D0→7F1) which is excited by xenon lamp with the wavelength of 200-280 nm, indicating that the Eu3+ ion mainly locates in the symmetric position (Oh) in the crystal lattice of CaO.展开更多
Sr2ScAlO5:Eu^2+, a red oxide phosphor with a perovskite-type structure, has been synthesized through a solid-state reaction and its luminescence properties have been investigated. An absorption band centering at 450...Sr2ScAlO5:Eu^2+, a red oxide phosphor with a perovskite-type structure, has been synthesized through a solid-state reaction and its luminescence properties have been investigated. An absorption band centering at 450 nm is observed from the diffuse reflection spectra and the excitation spectra, indicating that the phosphor can match perfectly with the blue light of InGaN light-emitting diodes. A broad red emission band at 620 nm is found from the emission spectra, originating from the 4f^65d-4f^7 transition of the Eu^2+ ions. The best doping content of Eu in this material is about 5%. S Sr2ScAlO5:Eu^2+ is a highly promising red phosphor for use in white light-emitting diodes.展开更多
Nanoparticles of red long afterglow phosphor Sr3Al2O6: Eu2+ were prepared by microwave irradiation method at a power of 680 W and a processing time of 15 min. The phosphors nanoparticles were characterized by X-ray di...Nanoparticles of red long afterglow phosphor Sr3Al2O6: Eu2+ were prepared by microwave irradiation method at a power of 680 W and a processing time of 15 min. The phosphors nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fluorescence spectrophotometer techniques. The results reveal that the samples are composed of single Sr3Al2O6 phase. The resultant nanoparticles show small size (80?100 nm) and spherical shape. The excitation and emission spectra indicate that excitation broad band chiefly lies in visible range and the nanoparticles emit much strong light at 612 nm under around 473 nm excitation. And the long afterglow phosphorescence of Sr3Al2O6 doped with Eu2+ was observed in the dark with naked eye after the removal of the excitation light. The effect of Eu2+ doping concentrations of the samples on the emission intensity is studied systematically. Furthermore, the microwave method requires a very short heating-time and the energy consumption.展开更多
A complete solid solutions with monophasic zircon-type structure of vanadates of formula GdxBio.95-xVO4:0.05Eu3+ (x = 04).95) are synthesized by combined method of co-precipitation and hydrothermal synthesis. The...A complete solid solutions with monophasic zircon-type structure of vanadates of formula GdxBio.95-xVO4:0.05Eu3+ (x = 04).95) are synthesized by combined method of co-precipitation and hydrothermal synthesis. Their microstructures and morphologies are characterized by X-ray powder diffraction and transmission electronic microscope, and the results show that each of all the samples has a monophasic zircon-type structure. The absorption spectrum of the prepared phosphor shows a blue-shift of the fundamental absorption band edge with increasing the gadolinium content. Under UV-light and visible-light excitation, all the prepared phosphors show the typical luminescence properties of Eu3+ in the zircon-type structure. The emission intensity of GdxBi0.95-xVO4:0.05Eu3+ (x = 0.55) is strongest in all samples under UV-light and visible-light excitations. Finally, the mechanisms of luminescence of Eu3+ in the GdxBi0.95-xVO4:0.05Eu3+ (x = 0-0.95) solid solutions are analyzed and discussed.展开更多
In this paper,we demonstrate that controlled dopant-concentration is an essential issue for charge carriers transporting in red Phosphorescent Organic Light-Emitting Device(PHOLED).Carriers transport via dopant molecu...In this paper,we demonstrate that controlled dopant-concentration is an essential issue for charge carriers transporting in red Phosphorescent Organic Light-Emitting Device(PHOLED).Carriers transport via dopant molecules in the emitting layer with a single host,however,via both dopant and host molecules when their energy levels are well aligned.Conditions for reduced driving-voltage and enhanced efficiency of red PHOLED are obtained by employing a mixed host structure.A pure red PHOLED with color coordinates of(0.67,0.33) has been realized by using only 4 wt% dopant,The device achieves 100 cd/cm2 at 2.9 V,with corresponding power efficiency of 9.3 lm/W and external quantum efficiency of 14.3%.展开更多
Red emitting phosphor (BaCa)3 (PO4)2 : Ce, Mn was prepared by solid state reactions. Effect of chemical component, preparation conditions on the performance of the phosphor was studied by using TGDTG, XRD and pho...Red emitting phosphor (BaCa)3 (PO4)2 : Ce, Mn was prepared by solid state reactions. Effect of chemical component, preparation conditions on the performance of the phosphor was studied by using TGDTG, XRD and phosphor relative brightness meter. It is found that the host ( Bax Ca1-x ) 3 (PO4) 2 is present as a distorted Ca3(PO4)2 structure. Ce^3+ acts as a sensitiser, and Mn^2+ is activator. By energy transfer from Ce^3+ to Mn^2+, Mn^2+ is activated and emits red light with wavelength around 650 nm. The phosphor powder shows the highest emitting brightness, when the con- centrations of Ce^3+and Mn^2+ are both at 0.15 mol.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
基金Project is supported by National High Technology Research and Development Program of China (863 Program) (2002 AA 324060)National Natural Science Foundation of China (10404028)
文摘Sol-gel method was utilized to synthesize two different series of red silicate phosphors:MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3:Eu2+, Dy3+, Mn2+. TGA curves of the gel precursor for two series depicted that the loss of residual organic groups and NO3 groups occurs below 450 ℃. According to the XRD patterns, the major diffraction peaks of the MgSiO3 and Mg2SiO4 series are consistent with a proto-enstatite structure (JCPDS No.11-0273) and a forsterite structure (JCPDS No.85-1364) respectively. With the excitation at 415 nm, the red emission band of Mn2+ ions is peaked at 661 nm for MgSiO3:1%(atom fraction) Mn2+ or 644 nm for Mg2SiO4:1%(atom fraction) Mn2+. Compared with Mg2SiO4:Mn2+ samples, MgSiO3:Mn2+ samples exhibit higher luminescence intensity and higher quenching concentration. In addition, the two series co-doped with Eu2+, Dy3+, Mn2+ were also prepared. Photo-luminescence and afterglow properties of the two co-doped series were analyzed, which show that MgSiO3:Eu2+, Dy3+, Mn2+ is more suitable for a red long-lasting phosphor.
基金Project supported by the Key Research Project of Science and Technology of Shanxi, Shanxi Province, China (Grant No 2007031141)the Natural Science Foundation of Shanxi Province, China (Grant No 2007011061)the Scientific Research Foundation of the Higher Education Institutions of Shanxi Province, China (Grant No 20080012)
文摘A type of red luminescent Sr3Al2O6:Eu2+, Dy3+ phosphor powder is synthesised by sol-gel-combustion processing, with metal nitrates used as the source of metal ions and citric acid as a chelating agent of metal ions. By tracing the formation process of the sol-gel, it is found that it is necessary to reduce the amount of NO3 by dropping ethanol into the solution for forming a stable and homogeneous sol-gel. Thermogravimetric and Differential Scanning Calorimeter Analysis, x-ray diffractionmeter, scanning electron microscopy and photoluminescence spectroscopy are used to investigate the luminescent properties of the as-synthesised Sr3A1206:Eu2+, Dy3+. The results reveal that the Sr3Al2O6 crystallises completely when the combustion ash is sintered at 1250℃. The excitation and the emission spectra indicate that the excitation broadband lies mainly in a visible range and the phosphors emit a strong light at 618 nm under the excitation of 472 nm. The afterglow of (Sr0.94Eu0.03Dy0.03)3Al2O6 phosphors sintered at 1250℃ lasts for over 1000 s when the excited source is cut off.
基金supported by the Program for New Material Development & Application innovative Research Team of Higher Education in Chong Qing of China (Grant No. 201042)
文摘A series of(Y_(1-y), Gdy)_(0.95-x)(P_y, V_(1-y))O_4 :0.05Eu^(3+), xBi^(3+)+phosphors have been successfully prepared by a subsection method. The crystal structure, surface morphology and luminescence properties were investigated. It was found that the sintered samples crystallized in a tetragonal crystal system with space group I_(41)/amd(a = b = 0.7119 nm, c = 0.6290 nm). The products presented rod-like morphology with length of 100-150 nm and width of 50-100 nm. A maximum peak at 619 nm(~5D_0 →~7F_2) was observed in emission spectrum of the phosphors. It was also found that co-doping of Bi^(3+)+, P5+and Gd^(3+)ions into YVO_4:Eu^(3+)can not only made the right edge of the excitation band shift to the long-wavelength region, but also increased the emission intensity at 619 nm sharply and decreased the lifetime of fluorescence decay. These results may expand the application scope of the phosphors.
文摘A series of (SrNa)2-xEux(MoO4)3 red phosphors have been synthesized by using the sol-gel method. X-ray diffraction, used to characterize the crystallization process of the phosphor precursors, indicates that the (SrNa)2-xEux(MoO4)3 phosphors had an SrMoO4 structure. The properties of these resulting phosphors have also been characterized by using photoluminescence (PL) spectra. The PL results indicate that all of the (SrNa)2-xEux(MoO4)3 phosphors exhibit intense red emissions under 275, 395, and 465-nm excitation. The two strongest lines at 395 and 465 nm in the excitation spectra of these phosphors match well with the two popular emissions from near-UV and blue GaN-based light-emitting diodes. Some process parameters for Eu3+ concentration, (C6H8O7)·H2O concentration, and solution pH value were also investigated. For (SrNa)2-xEux(MoO4)3 phosphors, there are two maximum emission intensities appearing with x = 0.6 and x = 1.4, respectively. When the molar ratio of citric acid is equal to that of metal cations and the solution pH is almost 4, (SrNa)2-xEux(MoO4)3 shows the strongest emission intensity compared to those under other conditions.
基金supported by Jiangxi Provincial Department of Education (GJJ08344)
文摘The luminescent properties of Eu^3+doped Ca2SiO4 red phosphors synthesized by the flux fusion reaction method were investigated. It was found that the excitation spectrum included two regions: the weak excitation band below 325 nm and strong narrow peaks above 325 nm. The main peak of the excitation band was located at 400 nm. The peaks located at 290 nm were assigned to the combination of the charge transfer transition of O-Eu, peaks above 325 nm (325, 385, 400, 470, 511, and 539 nm) were assigned to the f-f transitions of Eu^3+. The emission spectrum was dominated by the red peak located at 612 nm due to the electric dipole transition of ^5D0-^7F2. In addition, the effects of the Eu^3+ content and charge compensators of Li^+, Na^+, K^+, and Cl^- ions on the emission intensity were investigated. The experiment results suggested that the strongest emission was obtained when the concentration of the Eu^3+ ions was 0.3 mol^-1, and Li^+ ions gave the best improvement to enhance the emission intensity. Ca2SiO4:Eu^3+, Li^+ was thus suitable for low-cost trichromatic white light emitting diodes (WLED) based on UV InGaN chip.
基金Project supported by MOST of China (2006CB601104)Synchrotron Radiation Fund of Innovation Project of Ministry of Education (20041213S)
文摘Red phosphor (Y, Gd)BO3:Eu3+ with grain shape, small size, non-agglomerate, high crystallinity and good photoluminescence (PL) intensity was prepared by a complex method that the precursor of the phosphor was prepared by co-precipitation method and the phosphor was prepared by combustion method. The SEM photos and the photoluminescence spectrum excited under VUV show that the morphology and luminescent properties of this phosphor are satisfied when an appropriate amount of urea was adopted as the combustion agent in the preparation procedure.
基金Funded by the Science and Technology Bureau of Sichun Province(No.2006J13-059)Education Bureau of Sichun Province (No. 2006A094)
文摘Ca(NO3)2·4H2O, Eu(NO3)3 and H2C2O4·2H2O were adopted to synthesize CaO: Eu3+ with the chemical co-precipitation method, and the effects of the calcination temperature and Eu3+ doping concentration on the phosphor structure and its luminescent properties were investigated by TG-SDTA, XRD, and PL-PLE. The results confirm that the Eu3+ ions as luminescent centers substi-tutes Ca2+ sites without changing the crystal structure of cubic CaO. The optimum calcination tem-perature and the optimum concentration of Eu3+ are 1 100 ℃ and 1 mol%, respectively, under which the best crystallinity and highest PL intensity appeared. The maximum emission wavelength is 592 nm (5D0→7F1) which is excited by xenon lamp with the wavelength of 200-280 nm, indicating that the Eu3+ ion mainly locates in the symmetric position (Oh) in the crystal lattice of CaO.
基金Project supported by the National Natural Science Foundation of China (Grant No. 90922027)the National High Technology Research and Development Program of China (Grant No. 2009AA03Z432)
文摘Sr2ScAlO5:Eu^2+, a red oxide phosphor with a perovskite-type structure, has been synthesized through a solid-state reaction and its luminescence properties have been investigated. An absorption band centering at 450 nm is observed from the diffuse reflection spectra and the excitation spectra, indicating that the phosphor can match perfectly with the blue light of InGaN light-emitting diodes. A broad red emission band at 620 nm is found from the emission spectra, originating from the 4f^65d-4f^7 transition of the Eu^2+ ions. The best doping content of Eu in this material is about 5%. S Sr2ScAlO5:Eu^2+ is a highly promising red phosphor for use in white light-emitting diodes.
基金Project (50072014) supported by the National Natural Science Foundation of China
文摘Nanoparticles of red long afterglow phosphor Sr3Al2O6: Eu2+ were prepared by microwave irradiation method at a power of 680 W and a processing time of 15 min. The phosphors nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fluorescence spectrophotometer techniques. The results reveal that the samples are composed of single Sr3Al2O6 phase. The resultant nanoparticles show small size (80?100 nm) and spherical shape. The excitation and emission spectra indicate that excitation broad band chiefly lies in visible range and the nanoparticles emit much strong light at 612 nm under around 473 nm excitation. And the long afterglow phosphorescence of Sr3Al2O6 doped with Eu2+ was observed in the dark with naked eye after the removal of the excitation light. The effect of Eu2+ doping concentrations of the samples on the emission intensity is studied systematically. Furthermore, the microwave method requires a very short heating-time and the energy consumption.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB211708)the National Natural Science Foundation of China(Grant Nos.51272097,61265004,and 61307111)the Natural Science Foundation of Yunnan Province,China(Grant No.2012FD009)
文摘A complete solid solutions with monophasic zircon-type structure of vanadates of formula GdxBio.95-xVO4:0.05Eu3+ (x = 04).95) are synthesized by combined method of co-precipitation and hydrothermal synthesis. Their microstructures and morphologies are characterized by X-ray powder diffraction and transmission electronic microscope, and the results show that each of all the samples has a monophasic zircon-type structure. The absorption spectrum of the prepared phosphor shows a blue-shift of the fundamental absorption band edge with increasing the gadolinium content. Under UV-light and visible-light excitation, all the prepared phosphors show the typical luminescence properties of Eu3+ in the zircon-type structure. The emission intensity of GdxBi0.95-xVO4:0.05Eu3+ (x = 0.55) is strongest in all samples under UV-light and visible-light excitations. Finally, the mechanisms of luminescence of Eu3+ in the GdxBi0.95-xVO4:0.05Eu3+ (x = 0-0.95) solid solutions are analyzed and discussed.
基金the National Hi-Tech Research and Development Program of China,the Ministry of Science and Technology of China,the National Natural Science Foundation of China,the Research Fund for the Doctoral Program of Higher Education,the Scientific and Technological Developing Scheme of Jilin Province
文摘In this paper,we demonstrate that controlled dopant-concentration is an essential issue for charge carriers transporting in red Phosphorescent Organic Light-Emitting Device(PHOLED).Carriers transport via dopant molecules in the emitting layer with a single host,however,via both dopant and host molecules when their energy levels are well aligned.Conditions for reduced driving-voltage and enhanced efficiency of red PHOLED are obtained by employing a mixed host structure.A pure red PHOLED with color coordinates of(0.67,0.33) has been realized by using only 4 wt% dopant,The device achieves 100 cd/cm2 at 2.9 V,with corresponding power efficiency of 9.3 lm/W and external quantum efficiency of 14.3%.
文摘Red emitting phosphor (BaCa)3 (PO4)2 : Ce, Mn was prepared by solid state reactions. Effect of chemical component, preparation conditions on the performance of the phosphor was studied by using TGDTG, XRD and phosphor relative brightness meter. It is found that the host ( Bax Ca1-x ) 3 (PO4) 2 is present as a distorted Ca3(PO4)2 structure. Ce^3+ acts as a sensitiser, and Mn^2+ is activator. By energy transfer from Ce^3+ to Mn^2+, Mn^2+ is activated and emits red light with wavelength around 650 nm. The phosphor powder shows the highest emitting brightness, when the con- centrations of Ce^3+and Mn^2+ are both at 0.15 mol.
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.