Ho^3＋-doped titanium dioxide（TiO2：Ho^3＋） downconversion（DC） nanowires were synthesized through a simple hydrothermal method followed by a subsequent calcination process after being immersed in Ho（NO3）3 aqueou...Ho^3＋-doped titanium dioxide（TiO2：Ho^3＋） downconversion（DC） nanowires were synthesized through a simple hydrothermal method followed by a subsequent calcination process after being immersed in Ho（NO3）3 aqueous solution. Moreover, TiO2：Ho^3＋ nanowires（HTNWs） were used as the photoanode in dye-sensitized solar cells（DSSCs） to investigate their photoelectric properties. Scanning electron microscopy（SEM） and X-ray diffraction（XRD） were used to characterize the morphology and structure of the material, respectively. The photofluorescence and ultraviolet-visible absorption spectra of HTNWs reveal a DC from the near and middle ultraviolet light to visible light which matches the strong absorbed region of the N719 dye. Compared with the pure TNW photoanode, HTNWs DC photoanodes show greater photovoltaic efficiency. The photovoltaic conversion efficiency（η） of the DSSCs with HTNWs photoanode doped with 4% Ho2O3（mass fraction） is two times that with pure TNW photoanode. This enhancement could be attributed to HTNWs which could extend the spectral response range of DSSCs to the near and middle ultraviolet region and increase the short-circuit current density（Jsc） of DSSCs, thus leading to the enhancement of photovoltaic conversion efficiency.展开更多
Bi3＋ and Yb3＋ codoped cubic Y2O3 phosphors are prepared by pechini sol-gel method. Strong near-infrared （NIR） emission around 980 nm from Yb3＋ （2F5/2＋2 F7/2） is observed under ultraviolet light excitation. A b...Bi3＋ and Yb3＋ codoped cubic Y2O3 phosphors are prepared by pechini sol-gel method. Strong near-infrared （NIR） emission around 980 nm from Yb3＋ （2F5/2＋2 F7/2） is observed under ultraviolet light excitation. A broad excitation band ranging from 320 to 360 nm, owing to the 6s2→6s6p transition of Bi3＋ ions, is recorded when the Yb3＋ emission is monitored, which suggests a very efficient energy transfer from Bi3＋ ions to Yb3＋ ions. The Yb3＋ concentration dependences of both the Bi3＋ and the Yb3＋ emissions are investigated. The decay curve of Bi3＋ emission under the excitation of 355 nm pulse laser is used to explore the Bi3＋ →＋Yb3＋ energy transfer process. Cooperative energy transfer （CET） is discussed as a possible mechanism for the near-infrared emission.展开更多
All of the samples were synthesized by sol-gel methods.Two approaches to charge compensation,（i） 2Ca2＋→Yb3＋＋M＋,where M＋ is an alkali ion like Li＋,Na＋ and K＋,and（ii） indirect charge compensation：3Ca2＋→2...All of the samples were synthesized by sol-gel methods.Two approaches to charge compensation,（i） 2Ca2＋→Yb3＋＋M＋,where M＋ is an alkali ion like Li＋,Na＋ and K＋,and（ii） indirect charge compensation：3Ca2＋→2Yb3＋＋vacancy,were studied in detail.It was found that charge compensation would be very beneficial for the growth of the grains,especially in Li＋ ions added samples.All the grains were homogeneously spherical with less boundaries;in addition,a great variety of the absorption ability in different charge compensation samples were observed：in comparison with the phosphors without charge compensation,indirectly charge compensated and Li＋ ions added phosphors showed much stronger absorption strength in the ultraviolet（UV） region whereas that of Na＋ and K＋ ions added samples was much weaker;moreover,measurements of the emission intensities showed that：in comparison with the phosphors without charge compensation,the visible emission intensity from MoO42-decreased a lot in indirectly charge compensated and Li＋ ions added phosphors,whereas there was a remarkable increase of the near infrared（NIR） emission intensity from Yb3＋ ions in the two types of samples under 266 nm excitation,implying more efficient energy transfer（ET） from MoO42-to Yb3＋ ions;at last,measurements and analysis of the decay curves of the visible 495 nm emission were carried out,and it was found that the energy transfer from MoO42-to Yb3＋ ions were more efficient in the two above types of phosphors.The theoretical quantum cutting（QC） efficiency was also improved greatly.Overall,the addition of Li＋ ions would be very beneficial for the morphology of the powders in addition to the growth of the grains.It was advantageous to increase the downconversion（DC） quantum efficiency;however,indirect charge compensation would enhance the NIR emission intensity to the most for its strongest absorption ability in the UV region.展开更多
Tb3＋ and Yb3＋ codoped Lu2O3 nanophosphors were synthesized by the reverse-strike co-precipitation method. The obtained Lu2O3：Tb3＋,Yb3＋ nanophosphors were characterized by X-ray diffraction （XRD） and photolumine...Tb3＋ and Yb3＋ codoped Lu2O3 nanophosphors were synthesized by the reverse-strike co-precipitation method. The obtained Lu2O3：Tb3＋,Yb3＋ nanophosphors were characterized by X-ray diffraction （XRD） and photoluminescence （PL） spectra. The XRD results showed that all the prepared nanophosphors could be readily indexed to pure cubic phase of Lu2O3 and indicated good crystallinity. The Tb3＋→Yb3＋ energy transfer mechanisms in the UV-blue region in Lu2O3 nanophosphors were investigated. The experimental results showed that the strong visible emission around 543 nm from Tb3＋ （5D4→7F5） and near-infrared （NIR） emission around 973 nm from Yb3＋ （2F5/2→2F7/2） of Lu2O3：Tb3＋,Yb3＋ nanophosphors were observed under ultraviolet light excitation, respectively. Tb3＋ could be effectively excited up to its 4f75d1 state and relaxed down to the 5D4 level, from which the energy was transferred cooperatively to two neighboring Yb3＋. The Yb3＋ concentration dependent luminescent properties and lifetimes of both the visible and NIR emissions were also studied. The lifetime of the visible emission decreased with the increase of Yb3＋ concentration, verifying the efficient energy transfer from the Tb3＋ to the Yb3＋. Cooperative energy transfer （CET） from Tb3＋ to Yb3＋ was discussed as a possible mechanism for the near-infrared emission. When doped concentrations were 1 mol.% Tb3＋ and 2 mol.% Yb3＋, the intensity of NIR emission was the strongest.展开更多
An efficient near-infrared （NIR） downconversion （DC） by converting broadband ultraviolet （UV） into NIR was demon- strated in YVO4：Tma＋,yb3＋ phosphors. The phosphors were extensively characterized using variou...An efficient near-infrared （NIR） downconversion （DC） by converting broadband ultraviolet （UV） into NIR was demon- strated in YVO4：Tma＋,yb3＋ phosphors. The phosphors were extensively characterized using various methods such as X-ray diffrac- tion, photoluminescence excitation, photoluminescence spectra and decay lifetime to provide supporting evidence for DC process. Upon UV light varying from 260 to 350 nm or blue light （473 nm） excitation, an intense NIR emission of Yb3＋ corresponding to tran- sition of 2Fs/2/5→2F7/2 peaking at 985 nm was generated. The visible emission, the NIR mission and the decay lifetime of the phosphors of various Yb3＋ concentrations were investigated. Experimental results showed that the energy transfer from vanadate group to Yb3＋ via Tm3＋ was very efficient. Application of the broadband DC YVO4：Tma＋,yb3＋ phosphors might greatly enhance response of sili- con-based solar cells.展开更多
A novel near-infrared （NIR） downconversion （DC） phosphor KSrPO4：Eu2＋, Pr3＋ is synthesized by the conventional high temperature solid-state reaction. The Eu2＋ acts as an efficient sensitizer for Pr3＋ in the KS...A novel near-infrared （NIR） downconversion （DC） phosphor KSrPO4：Eu2＋, Pr3＋ is synthesized by the conventional high temperature solid-state reaction. The Eu2＋ acts as an efficient sensitizer for Pr3＋ in the KSrPO4 host. With broad- band near-ultraviolet light excitation induced by the 4f→5d transition of Eu2＋, the characteristic NIR emission of Pr3＋, peaking at 974 nm and 1019 nm due to 3po →1G4 and 1G4→3H4 transitions, is generated as a result of the energy transfer from Eu2＋ to Pr3＋. The luminescence spectra in both the visible and the NIR regions and the decay lifetime curves of Eu2＋ prove the energy transfer from Eu2＋ to Pr3＋. This Eu2＋ and Pr3＋ co-doped KSrPO4 phosphor may be a promising candidate to modify the spectral mismatch behavior of crystalline solar cells and sunlight.展开更多
The wide-band digital receiving systems require digital downconversion(DDC) with high data rate and short tuning time in order to intercept the narrow-band signals within broad tuning bandwidth. But these requirements...The wide-band digital receiving systems require digital downconversion(DDC) with high data rate and short tuning time in order to intercept the narrow-band signals within broad tuning bandwidth. But these requirements can not be met by the commercial DDC. In this paper an efficient implementation architecture is presented. It combines the flexibility of DFT tuning with the efficiency of the polyphase filter bank decomposition. By first decimating the data prior to filtering and mixing, this architecture gives a better solution to the mismatch between the lower hardware speed and high data rate. The computer simulations show the feasibility of this processing architecture.展开更多
During the downconversion process,a high-energy photon undergoes conversion into several low-energy photons,leading to enhanced luminous efficiency in both photoluminescent and electroluminescent devices.This phenomen...During the downconversion process,a high-energy photon undergoes conversion into several low-energy photons,leading to enhanced luminous efficiency in both photoluminescent and electroluminescent devices.This phenomenon has been applied in various fields,including solar cells,plasma display panels,and green lighting technologies such as mercury-free fluorescent lamps.However,the concept of downconversion(quantum cutting)has not been fully explored in the context of mechanoluminescent materials.In this study,we successfully synthesized a heterojunction of CaF_(2)/CaZnOS exhibiting efficient downconversion mechanoluminescence(ML)properties.By controlling the CaF_(2)to CaZnOS ratio and incorporating Tb^(3+)doping,we obtained a highly effective heterojunction structure that significantly enhanced ML.Moreover,we extended this material to several commonly utilized downconversion ion-doping combinations,achieving enhanced ML for Tb^(3+),Pr^(3+),and Yb^(3+)single ions.For the first time,we demonstrate the downconversion(quantum cutting)ML of Tb^(3+)-Yb^(3+)and Pr^(3+)-Yb^(3+)pairs within heterojunction microstructures.This study presents the design and synthesis of a novel heterojunction material capable of realizing downconversion ML,which holds promise for future applications in diverse fields.展开更多
基金Project(2012FU125X03)supported by Open Research Fund Project of National Engineering Research Center of SeafoodChina+3 种基金Project(2011–191)supported by the Key Science and Technology Platform of Liaoning Provincial Education DepartmentChinaProject(2010–354)supported by the Science and Technology Platform of DalianChina
文摘Ho^3＋-doped titanium dioxide（TiO2：Ho^3＋） downconversion（DC） nanowires were synthesized through a simple hydrothermal method followed by a subsequent calcination process after being immersed in Ho（NO3）3 aqueous solution. Moreover, TiO2：Ho^3＋ nanowires（HTNWs） were used as the photoanode in dye-sensitized solar cells（DSSCs） to investigate their photoelectric properties. Scanning electron microscopy（SEM） and X-ray diffraction（XRD） were used to characterize the morphology and structure of the material, respectively. The photofluorescence and ultraviolet-visible absorption spectra of HTNWs reveal a DC from the near and middle ultraviolet light to visible light which matches the strong absorbed region of the N719 dye. Compared with the pure TNW photoanode, HTNWs DC photoanodes show greater photovoltaic efficiency. The photovoltaic conversion efficiency（η） of the DSSCs with HTNWs photoanode doped with 4% Ho2O3（mass fraction） is two times that with pure TNW photoanode. This enhancement could be attributed to HTNWs which could extend the spectral response range of DSSCs to the near and middle ultraviolet region and increase the short-circuit current density（Jsc） of DSSCs, thus leading to the enhancement of photovoltaic conversion efficiency.
基金supported by the National Nature Science Foundation of China (Grant No. 10774140)the Knowledge Innovation Project of the Chinese Academy of Sciences (Grant No. KJCX2-YW-M11)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No. 20060358054)the Special Foundation for Talents of Anhui Province,China (GrantNo. 2007Z021)
文摘Bi3＋ and Yb3＋ codoped cubic Y2O3 phosphors are prepared by pechini sol-gel method. Strong near-infrared （NIR） emission around 980 nm from Yb3＋ （2F5/2＋2 F7/2） is observed under ultraviolet light excitation. A broad excitation band ranging from 320 to 360 nm, owing to the 6s2→6s6p transition of Bi3＋ ions, is recorded when the Yb3＋ emission is monitored, which suggests a very efficient energy transfer from Bi3＋ ions to Yb3＋ ions. The Yb3＋ concentration dependences of both the Bi3＋ and the Yb3＋ emissions are investigated. The decay curve of Bi3＋ emission under the excitation of 355 nm pulse laser is used to explore the Bi3＋ →＋Yb3＋ energy transfer process. Cooperative energy transfer （CET） is discussed as a possible mechanism for the near-infrared emission.
基金Project supported by the National Natural Science Foundation of China (10774140,11074245,11011120083)Knowledge Innovation Project of the Chinese Academy of Sciences (KJCX2-YW-M11)Special Foundation for Talents of Anhui Province,China (2007Z021)
文摘All of the samples were synthesized by sol-gel methods.Two approaches to charge compensation,（i） 2Ca2＋→Yb3＋＋M＋,where M＋ is an alkali ion like Li＋,Na＋ and K＋,and（ii） indirect charge compensation：3Ca2＋→2Yb3＋＋vacancy,were studied in detail.It was found that charge compensation would be very beneficial for the growth of the grains,especially in Li＋ ions added samples.All the grains were homogeneously spherical with less boundaries;in addition,a great variety of the absorption ability in different charge compensation samples were observed：in comparison with the phosphors without charge compensation,indirectly charge compensated and Li＋ ions added phosphors showed much stronger absorption strength in the ultraviolet（UV） region whereas that of Na＋ and K＋ ions added samples was much weaker;moreover,measurements of the emission intensities showed that：in comparison with the phosphors without charge compensation,the visible emission intensity from MoO42-decreased a lot in indirectly charge compensated and Li＋ ions added phosphors,whereas there was a remarkable increase of the near infrared（NIR） emission intensity from Yb3＋ ions in the two types of samples under 266 nm excitation,implying more efficient energy transfer（ET） from MoO42-to Yb3＋ ions;at last,measurements and analysis of the decay curves of the visible 495 nm emission were carried out,and it was found that the energy transfer from MoO42-to Yb3＋ ions were more efficient in the two above types of phosphors.The theoretical quantum cutting（QC） efficiency was also improved greatly.Overall,the addition of Li＋ ions would be very beneficial for the morphology of the powders in addition to the growth of the grains.It was advantageous to increase the downconversion（DC） quantum efficiency;however,indirect charge compensation would enhance the NIR emission intensity to the most for its strongest absorption ability in the UV region.
基金Project supported by National Natural Science Foundation of China (10774140, 11047147, 11074245, 11011120083)Knowledge Innovation Project of The Chinese Academy of Sciences (KJCX2-YW-M11)the Natural Science Foundation of Chongqing Municipal Education Commission (KJTD201016, KJ090514)
文摘Tb3＋ and Yb3＋ codoped Lu2O3 nanophosphors were synthesized by the reverse-strike co-precipitation method. The obtained Lu2O3：Tb3＋,Yb3＋ nanophosphors were characterized by X-ray diffraction （XRD） and photoluminescence （PL） spectra. The XRD results showed that all the prepared nanophosphors could be readily indexed to pure cubic phase of Lu2O3 and indicated good crystallinity. The Tb3＋→Yb3＋ energy transfer mechanisms in the UV-blue region in Lu2O3 nanophosphors were investigated. The experimental results showed that the strong visible emission around 543 nm from Tb3＋ （5D4→7F5） and near-infrared （NIR） emission around 973 nm from Yb3＋ （2F5/2→2F7/2） of Lu2O3：Tb3＋,Yb3＋ nanophosphors were observed under ultraviolet light excitation, respectively. Tb3＋ could be effectively excited up to its 4f75d1 state and relaxed down to the 5D4 level, from which the energy was transferred cooperatively to two neighboring Yb3＋. The Yb3＋ concentration dependent luminescent properties and lifetimes of both the visible and NIR emissions were also studied. The lifetime of the visible emission decreased with the increase of Yb3＋ concentration, verifying the efficient energy transfer from the Tb3＋ to the Yb3＋. Cooperative energy transfer （CET） from Tb3＋ to Yb3＋ was discussed as a possible mechanism for the near-infrared emission. When doped concentrations were 1 mol.% Tb3＋ and 2 mol.% Yb3＋, the intensity of NIR emission was the strongest.
基金Project supported by the National Key Basic Research Program of China (2013CB921800)the National Natural Science Foundation of China (11074245, 11204292, 11274299)the Fundamental Research Funds for the Central Universities (WK2030020022)
文摘An efficient near-infrared （NIR） downconversion （DC） by converting broadband ultraviolet （UV） into NIR was demon- strated in YVO4：Tma＋,yb3＋ phosphors. The phosphors were extensively characterized using various methods such as X-ray diffrac- tion, photoluminescence excitation, photoluminescence spectra and decay lifetime to provide supporting evidence for DC process. Upon UV light varying from 260 to 350 nm or blue light （473 nm） excitation, an intense NIR emission of Yb3＋ corresponding to tran- sition of 2Fs/2/5→2F7/2 peaking at 985 nm was generated. The visible emission, the NIR mission and the decay lifetime of the phosphors of various Yb3＋ concentrations were investigated. Experimental results showed that the energy transfer from vanadate group to Yb3＋ via Tm3＋ was very efficient. Application of the broadband DC YVO4：Tma＋,yb3＋ phosphors might greatly enhance response of sili- con-based solar cells.
基金Project supported by the National Natural Science Foundation of China (Grant No. 20976002)the Beijing Natural Science Foundation, China (Grant No. 2122012)the Special Funding of the Ministry of Education of Guangdong Province, China (Grant No. 2011B090400100)
文摘A novel near-infrared （NIR） downconversion （DC） phosphor KSrPO4：Eu2＋, Pr3＋ is synthesized by the conventional high temperature solid-state reaction. The Eu2＋ acts as an efficient sensitizer for Pr3＋ in the KSrPO4 host. With broad- band near-ultraviolet light excitation induced by the 4f→5d transition of Eu2＋, the characteristic NIR emission of Pr3＋, peaking at 974 nm and 1019 nm due to 3po →1G4 and 1G4→3H4 transitions, is generated as a result of the energy transfer from Eu2＋ to Pr3＋. The luminescence spectra in both the visible and the NIR regions and the decay lifetime curves of Eu2＋ prove the energy transfer from Eu2＋ to Pr3＋. This Eu2＋ and Pr3＋ co-doped KSrPO4 phosphor may be a promising candidate to modify the spectral mismatch behavior of crystalline solar cells and sunlight.
文摘The wide-band digital receiving systems require digital downconversion(DDC) with high data rate and short tuning time in order to intercept the narrow-band signals within broad tuning bandwidth. But these requirements can not be met by the commercial DDC. In this paper an efficient implementation architecture is presented. It combines the flexibility of DFT tuning with the efficiency of the polyphase filter bank decomposition. By first decimating the data prior to filtering and mixing, this architecture gives a better solution to the mismatch between the lower hardware speed and high data rate. The computer simulations show the feasibility of this processing architecture.
基金supported by the Natural Science Foundation of China(62275170)the Key-Area Research and Development Program of Guangdong Province(2024B0101080001)+4 种基金the Guangdong Provincial Science Fund for Distinguished Young Scholars(2022B1515020054)Shenzhen Fundamental Research Project(JCYJ20240813141624033)Scientific Research Foundation as Phase III construction of high-level University 2035 plan(0000050101)the proof-of-concept project of Shenzhen University(000003011313)as well as Medical-Engineering Interdisciplinary Research Foundation of ShenZhen University(2023YG031).
文摘During the downconversion process,a high-energy photon undergoes conversion into several low-energy photons,leading to enhanced luminous efficiency in both photoluminescent and electroluminescent devices.This phenomenon has been applied in various fields,including solar cells,plasma display panels,and green lighting technologies such as mercury-free fluorescent lamps.However,the concept of downconversion(quantum cutting)has not been fully explored in the context of mechanoluminescent materials.In this study,we successfully synthesized a heterojunction of CaF_(2)/CaZnOS exhibiting efficient downconversion mechanoluminescence(ML)properties.By controlling the CaF_(2)to CaZnOS ratio and incorporating Tb^(3+)doping,we obtained a highly effective heterojunction structure that significantly enhanced ML.Moreover,we extended this material to several commonly utilized downconversion ion-doping combinations,achieving enhanced ML for Tb^(3+),Pr^(3+),and Yb^(3+)single ions.For the first time,we demonstrate the downconversion(quantum cutting)ML of Tb^(3+)-Yb^(3+)and Pr^(3+)-Yb^(3+)pairs within heterojunction microstructures.This study presents the design and synthesis of a novel heterojunction material capable of realizing downconversion ML,which holds promise for future applications in diverse fields.
基金The National Natural Science Foundation of China(Nos.61275180,50972061,51272109)the Natural Science Foundation of Zhejiang Province(Nos.Z4110072,R4100364)+1 种基金the Opening Foundation of Zhejiang Provincial Top Key DisciplineK.C.Wang Magna Fund in Ningbo University
