The emission wavelength of current near-infrared phosphors activated by Cr^(3+)is generally smaller than 900 nm in near-infrared(NIR)Ⅰ region,and it is extremely challenging and is of great practical significance to ...The emission wavelength of current near-infrared phosphors activated by Cr^(3+)is generally smaller than 900 nm in near-infrared(NIR)Ⅰ region,and it is extremely challenging and is of great practical significance to realize emission towards NIR-Ⅱ region.In this study,a novel Cr^(3+)excited KSrScSi_(2)O_(7)silicate broad-band phosphor was prepared using the traditional solid-state method.Cr^(3+)resides in a weak crystal field in the KSrScSi_(2)O_(7)lattice and exhibits broad-band near-infrared emission at 984 nm,longer than those of most Cr^(3+)activated phosphors,under 493 nm blue light excitation.This is due to the stro ng charge polarization caused by the unique local coordination environment of the silicate matrix,which leads to a reduction in the crystal field splitting energy of the[ScO_(6)]octahedron where Cr^(3+)is located and the downward shift of the^(4)T_(2)energy level.The optimal doping concentration of Cr^(3+)is found to be 2 mol%,and the quenching mechanism is dipole-dipole interaction.Compared to the phosphors with similar emission wavelengths(λ_(em)>900 nm),KSrScSi_(2)O_(7):Cr^(3+)demonstrates outstanding advantages in various aspects of luminescent performance.The fabricated phosphor-converted light-emitting diode(pc-LED)is shown to have the potential for night vision and non-invasive imaging.Novel application of KSrScSi_(2)O_(7):xCr^(3+)as stable green ceramic pigments is also explored.The KSrScSi_(2)O_(7):xCr^(3+)powders show a bright yellowish green appearance,and the KSrScSi_(2)O_(7):0.02Cr^(3+)typical composition has chromaticity values of L^(*)=82.73,a^(*)=-8.53,b^(*)=7.97.Remarkably,the glazing samples using KSrScSi_(2)O_(7):xCr^(3+)as pigments well retain the bright color after 1200℃sintering in different atmospheres.Therefore,multifunctional applications of KSrScSi_(2)O_(7):xCr^(3+)for near-infrared spectroscopy and as ceramic pigments are achieved in this work.展开更多
Cr^(3+)-activated near-infrared(NIR)phosphors are key for NIR phosphor-converted light emitting diodes(NIR pc-LED).While,the site occupancy of Cr^(3+)is one of the debates that have plagued researchers.Herein,Y2Mg2Al2...Cr^(3+)-activated near-infrared(NIR)phosphors are key for NIR phosphor-converted light emitting diodes(NIR pc-LED).While,the site occupancy of Cr^(3+)is one of the debates that have plagued researchers.Herein,Y2Mg2Al2-Si_(2)O1_(2)(YMAS)with multiple cationic sites is chosen as host of Cr^(3+)to synthesize YMAS:xCr^(3+)phosphors.In YMAS,Cr^(3+)ions occupy simultaneously Al/SiO4 tetrahedral,Mg/AlO6 octahedral,and Y/MgO8 dodecahedral sites which form three luminescent centers named as Cr1,Cr2,and Cr3,respectively.Cr1 and Cr2 relate to an intermediate crystal field,with transitions of^(2)E→^(4)A_(2)and^(4)T_(2)→^(4)A_(2)occurring simultaneously.As Cr^(3+)concentration increases,the^(4)T_(2)→^(4)A_(2)transition becomes more pronounced in Cr1 and Cr2,resulting in a red-shift and broadband emission.Cr3 consistently behaves a weak crystal field and exhibits the broad and long-wavelength emission.Wide-range NIR emission centering at 745 nm is realized in YMAS:0.03Cr^(3+)phosphor.This phosphor has high internal quantum efficiency(IQE?86%)and satisfying luminescence thermal stability(I423 K?70.2%).Using this phosphor,NIR pc-LEDs with 56.6 mW@320 mA optical output power is packaged and applied.Present study not only demonstrates the Cr^(3+)multi-site occupancy in a certain oxide but also provides a reliable approach via choosing a host with diverse cationic sites and local environments for Cr^(3+)to achieve broadband NIR phosphors.展开更多
Yb^(3+)-doped phosphors have characteristic near-infrared(NIR)emissions,but their applications in phosphor-converted light-emitting-diodes(pc-LEDs)and Si solar cells are limited due to their mismatching excitation spe...Yb^(3+)-doped phosphors have characteristic near-infrared(NIR)emissions,but their applications in phosphor-converted light-emitting-diodes(pc-LEDs)and Si solar cells are limited due to their mismatching excitation spectra.Here,we selected nitride La3 Si6 N11(LSN)as host material to achieve Yb^(3+)NIR emission upon low-energy charge transfer(CT)excitation.The obtained phosphor LSN:Yb^(3+)has a broad CT excitation band ranging from 250 to 500 nm and narrowband NIR emissions ranging from 950 to 1100 nm centered at 983 nm.On the basis of spectral data,the vacuum referred binding energies(VRBE)schemes are constructed to locate energy levels of all lanthanide ions in LSN.We also fabricated NIR pc-LED device using 395 nm LED chip to demonstrate the potential applications of LSN:Yb^(3+)phosphors.展开更多
In recent years,Fe^(3+)-doped near-infrared(NIR)phosphors have garnered significant attention,primarily due to their non-toxic nature,long emission wavelength,and excellent thermal stability.In this work,a series of N...In recent years,Fe^(3+)-doped near-infrared(NIR)phosphors have garnered significant attention,primarily due to their non-toxic nature,long emission wavelength,and excellent thermal stability.In this work,a series of NaBaScSi_(2)O_(7):xFe^(3+)(x=0.01-0.07)phosphors were synthesized by the conventional solid-state reaction method.The impact of Fe^(3+)doping on the bandgap of NaBaScSi_(2)O_(7)was analyzed by diffuse reflectance spectroscopy(DRS)and first-principles calculations.Under excitation at 301 nm,the series of phosphors emitted broadband NIR luminescence at 815 nm with full width at half maximum(FWHM)of 116 nm.Varying-temperature testing of the NaBaScSi_(2)O_(7):0.03Fe^(3+)phosphor indicated that it can retain 46%of its room temperature luminescence intensity at 423 K.This excellent thermal stability is attributed to the small Huang-Rhys factor(S),which results in weak electron-phonon coupling.In addition,the NIR phosphor-converted light-emitting diode(NIR pc-LED)integrated from the NaBaScSi_(2)O_(7):0.03Fe^(3+)optimal phosphor and a 310 nm ultraviolet(UV)chip showed a superior night vision capability.展开更多
For healthy lighting,daily lighting that considers both visible light and near-infrared(NIR)light is necessary.However,at~900 nm,the extensively used solar-like phosphor-converted light-emitting diodes(pc-LEDs)are lim...For healthy lighting,daily lighting that considers both visible light and near-infrared(NIR)light is necessary.However,at~900 nm,the extensively used solar-like phosphor-converted light-emitting diodes(pc-LEDs)are limited by a lack of high-performance NIR luminescent materials.We report a broadband NIR phosphor Sr_(2)ScSbO_(6):Cr^(3+) with a double perovskite-type structure,thus simultaneously demonstrating high luminescence efficiency and good thermal stability.Under 550-nm excitation,Sr_(2)ScSbO_(6):Cr^(3+) demonstrates broadband NIR emission centered at~890 nm with luminescence internal/external efficiencies of 82.0%/35.7%,respectively.Furthermore,the luminescence integrated intensity at 430 K remains at~66.4% of the initial intensity.We successfully fabricated pc-LED devices using a 465-nm-sized blue chip and other commercial phosphors,presenting a relatively complete solar-like spectrum from blue to NIR light and is expected to be used in solar-like lighting.展开更多
In this review, first, we discussed the effect of phosphor features on optical properties by the software simulation in detail. A combination of these parameters: phosphor material, phosphor particle size and particle...In this review, first, we discussed the effect of phosphor features on optical properties by the software simulation in detail. A combination of these parameters: phosphor material, phosphor particle size and particle distribution, phosphor layer concentration, phosphor layer thickness, geometry, and location of the phosphor layer, will result in the final optical performance of the phosphor layer. Secondly, we introduced how to improve light extraction efficiency with various proposed methods. Thirdly, we summarized the thermal models to predict the phosphor temperature and the junction temperature. To stabilize the optical performance of phosphor-converted light emitting diodes (PC-LEDs), much effort has been made to reduce the junction temperature of the LED chips. The phosphor temperature, a critical reliability concern for PC-LEDs, should be attracted academic interest. Finally, we summed up optical-thermal coupled model for phosphors and summarized future optical- thermal issues exploring the light quality for LEDs. We foresee that optical-thermal coupled model for PC-LEDs should be paid more attention in the future.展开更多
基金Project supported by the Natural Science Foundation of The Educational Department of Liaoning Province(JYTMS20231627)。
文摘The emission wavelength of current near-infrared phosphors activated by Cr^(3+)is generally smaller than 900 nm in near-infrared(NIR)Ⅰ region,and it is extremely challenging and is of great practical significance to realize emission towards NIR-Ⅱ region.In this study,a novel Cr^(3+)excited KSrScSi_(2)O_(7)silicate broad-band phosphor was prepared using the traditional solid-state method.Cr^(3+)resides in a weak crystal field in the KSrScSi_(2)O_(7)lattice and exhibits broad-band near-infrared emission at 984 nm,longer than those of most Cr^(3+)activated phosphors,under 493 nm blue light excitation.This is due to the stro ng charge polarization caused by the unique local coordination environment of the silicate matrix,which leads to a reduction in the crystal field splitting energy of the[ScO_(6)]octahedron where Cr^(3+)is located and the downward shift of the^(4)T_(2)energy level.The optimal doping concentration of Cr^(3+)is found to be 2 mol%,and the quenching mechanism is dipole-dipole interaction.Compared to the phosphors with similar emission wavelengths(λ_(em)>900 nm),KSrScSi_(2)O_(7):Cr^(3+)demonstrates outstanding advantages in various aspects of luminescent performance.The fabricated phosphor-converted light-emitting diode(pc-LED)is shown to have the potential for night vision and non-invasive imaging.Novel application of KSrScSi_(2)O_(7):xCr^(3+)as stable green ceramic pigments is also explored.The KSrScSi_(2)O_(7):xCr^(3+)powders show a bright yellowish green appearance,and the KSrScSi_(2)O_(7):0.02Cr^(3+)typical composition has chromaticity values of L^(*)=82.73,a^(*)=-8.53,b^(*)=7.97.Remarkably,the glazing samples using KSrScSi_(2)O_(7):xCr^(3+)as pigments well retain the bright color after 1200℃sintering in different atmospheres.Therefore,multifunctional applications of KSrScSi_(2)O_(7):xCr^(3+)for near-infrared spectroscopy and as ceramic pigments are achieved in this work.
基金supported by the National Natural Science Foundation of China(No.51772330)the Fundamental Research Funds for the Central Universities of Central South University(No.506021713)the National MCF Energy R&D Program of China(No.2018YFE0306100).
文摘Cr^(3+)-activated near-infrared(NIR)phosphors are key for NIR phosphor-converted light emitting diodes(NIR pc-LED).While,the site occupancy of Cr^(3+)is one of the debates that have plagued researchers.Herein,Y2Mg2Al2-Si_(2)O1_(2)(YMAS)with multiple cationic sites is chosen as host of Cr^(3+)to synthesize YMAS:xCr^(3+)phosphors.In YMAS,Cr^(3+)ions occupy simultaneously Al/SiO4 tetrahedral,Mg/AlO6 octahedral,and Y/MgO8 dodecahedral sites which form three luminescent centers named as Cr1,Cr2,and Cr3,respectively.Cr1 and Cr2 relate to an intermediate crystal field,with transitions of^(2)E→^(4)A_(2)and^(4)T_(2)→^(4)A_(2)occurring simultaneously.As Cr^(3+)concentration increases,the^(4)T_(2)→^(4)A_(2)transition becomes more pronounced in Cr1 and Cr2,resulting in a red-shift and broadband emission.Cr3 consistently behaves a weak crystal field and exhibits the broad and long-wavelength emission.Wide-range NIR emission centering at 745 nm is realized in YMAS:0.03Cr^(3+)phosphor.This phosphor has high internal quantum efficiency(IQE?86%)and satisfying luminescence thermal stability(I423 K?70.2%).Using this phosphor,NIR pc-LEDs with 56.6 mW@320 mA optical output power is packaged and applied.Present study not only demonstrates the Cr^(3+)multi-site occupancy in a certain oxide but also provides a reliable approach via choosing a host with diverse cationic sites and local environments for Cr^(3+)to achieve broadband NIR phosphors.
基金Project supported by National Natural Science Foundation of China(51832005,51972020)。
文摘Yb^(3+)-doped phosphors have characteristic near-infrared(NIR)emissions,but their applications in phosphor-converted light-emitting-diodes(pc-LEDs)and Si solar cells are limited due to their mismatching excitation spectra.Here,we selected nitride La3 Si6 N11(LSN)as host material to achieve Yb^(3+)NIR emission upon low-energy charge transfer(CT)excitation.The obtained phosphor LSN:Yb^(3+)has a broad CT excitation band ranging from 250 to 500 nm and narrowband NIR emissions ranging from 950 to 1100 nm centered at 983 nm.On the basis of spectral data,the vacuum referred binding energies(VRBE)schemes are constructed to locate energy levels of all lanthanide ions in LSN.We also fabricated NIR pc-LED device using 395 nm LED chip to demonstrate the potential applications of LSN:Yb^(3+)phosphors.
基金supported by the Natural Science Foundation of the Educational Department of Liaoning Province(Grant No.JYTMS20231627)the Natural Science Foundation of Liaoning Province(Grant No.2020-MS-286)the support from the"Young Talents Program"of Jinzhou。
文摘In recent years,Fe^(3+)-doped near-infrared(NIR)phosphors have garnered significant attention,primarily due to their non-toxic nature,long emission wavelength,and excellent thermal stability.In this work,a series of NaBaScSi_(2)O_(7):xFe^(3+)(x=0.01-0.07)phosphors were synthesized by the conventional solid-state reaction method.The impact of Fe^(3+)doping on the bandgap of NaBaScSi_(2)O_(7)was analyzed by diffuse reflectance spectroscopy(DRS)and first-principles calculations.Under excitation at 301 nm,the series of phosphors emitted broadband NIR luminescence at 815 nm with full width at half maximum(FWHM)of 116 nm.Varying-temperature testing of the NaBaScSi_(2)O_(7):0.03Fe^(3+)phosphor indicated that it can retain 46%of its room temperature luminescence intensity at 423 K.This excellent thermal stability is attributed to the small Huang-Rhys factor(S),which results in weak electron-phonon coupling.In addition,the NIR phosphor-converted light-emitting diode(NIR pc-LED)integrated from the NaBaScSi_(2)O_(7):0.03Fe^(3+)optimal phosphor and a 310 nm ultraviolet(UV)chip showed a superior night vision capability.
基金supported by the National Natural Science Foundation of China(51972020 and 51832005)。
文摘For healthy lighting,daily lighting that considers both visible light and near-infrared(NIR)light is necessary.However,at~900 nm,the extensively used solar-like phosphor-converted light-emitting diodes(pc-LEDs)are limited by a lack of high-performance NIR luminescent materials.We report a broadband NIR phosphor Sr_(2)ScSbO_(6):Cr^(3+) with a double perovskite-type structure,thus simultaneously demonstrating high luminescence efficiency and good thermal stability.Under 550-nm excitation,Sr_(2)ScSbO_(6):Cr^(3+) demonstrates broadband NIR emission centered at~890 nm with luminescence internal/external efficiencies of 82.0%/35.7%,respectively.Furthermore,the luminescence integrated intensity at 430 K remains at~66.4% of the initial intensity.We successfully fabricated pc-LED devices using a 465-nm-sized blue chip and other commercial phosphors,presenting a relatively complete solar-like spectrum from blue to NIR light and is expected to be used in solar-like lighting.
文摘In this review, first, we discussed the effect of phosphor features on optical properties by the software simulation in detail. A combination of these parameters: phosphor material, phosphor particle size and particle distribution, phosphor layer concentration, phosphor layer thickness, geometry, and location of the phosphor layer, will result in the final optical performance of the phosphor layer. Secondly, we introduced how to improve light extraction efficiency with various proposed methods. Thirdly, we summarized the thermal models to predict the phosphor temperature and the junction temperature. To stabilize the optical performance of phosphor-converted light emitting diodes (PC-LEDs), much effort has been made to reduce the junction temperature of the LED chips. The phosphor temperature, a critical reliability concern for PC-LEDs, should be attracted academic interest. Finally, we summed up optical-thermal coupled model for phosphors and summarized future optical- thermal issues exploring the light quality for LEDs. We foresee that optical-thermal coupled model for PC-LEDs should be paid more attention in the future.
基金supported by the National Key R&D Program of China (2021YFB3500400)the Autonomous Deployment Project of Haixi Institute,Chinese Academy of Sciences (CXZX-2022-GH11)。
