The vacancy-ordered quadruple perovskite Cs_(4)CdBi_(2)Cl_(12),as a newly-emerging lead-free perovskite system,has attracted great research interest due to its excellent stability and direct band gap.However,the poor ...The vacancy-ordered quadruple perovskite Cs_(4)CdBi_(2)Cl_(12),as a newly-emerging lead-free perovskite system,has attracted great research interest due to its excellent stability and direct band gap.However,the poor luminescence performance limits its application in light-emitting diodes(LEDs)and other fields.Herein,for the first time,an Ag^(+)ion doping strategy was proposed to greatly improve the emission performance of Cs_(4)CdBi_(2)Cl_(12) synthesized by hydrothermal method.Density functional theory calculations combined with experimental results evidence that the weak orange emission from Cs_(4)CdBi_(2)Cl_(12) is attributed to the phonon scattering and energy level crossing due to the large lattice distortion under excited states.Fortunately,Ag^(+)ion doping breaks the intrinsic crystal field environment of Cs_(4)CdBi_(2)Cl_(12),suppresses the crossover between ground and excited states,and reduces the energy loss in the form of nonradiative recombination.At a critical doping amount of 0.8%,the emission intensity of Cs_(4)CdBi_(2)Cl_(12):Ag^(+)reaches the maximum,about eight times that of the pristine sample.Moreover,the doped Cs_(4)CdBi_(2)Cl_(12) still maintains excellent stability against heat,ultraviolet irradiation,and environmental oxygen/moisture.The above advantages make it possible for this material to be used as solid-state phosphors for white LEDs applications,and the Commission International de I’Eclairage color coordinates of(0.31,0.34)and high color rendering index of 90.6 were achieved.More importantly,the white LED demonstrates remarkable operation stability in air ambient,showing almost no emission decay after a long working time for 48 h.We believe that this study puts forward an effective ion-doping strategy for emission enhancement of vacancy-ordered quadruple perovskite Cs_(4)CdBi_(2)Cl_(12),highlighting its great potential as efficient emitter compatible for practical applications.展开更多
Rare earth ions(RE^(3+))-doped double perovskites have attracted tremendous attention for its fascinating optical properties.Nevertheless,RE^(3+)generally exhibits poor photoluminescence quantum yield(PLQY)for their p...Rare earth ions(RE^(3+))-doped double perovskites have attracted tremendous attention for its fascinating optical properties.Nevertheless,RE^(3+)generally exhibits poor photoluminescence quantum yield(PLQY)for their parity-forbidden 4f-4f transition and the low doping concentration.Herein,we reported Sb^(3+)/Sm^(3+)-codoped rare earth-based double perovskite Cs_(2)Na Lu Cl_(6)that enables efficient visible and nearinfrared(NIR)emission,which stems from self-trapped exciton(STE)and Sm^(3+),respectively.Benefit from up to 72.89%energy transfer efficiency from STE to Sm^(3+)and high doping concentrations due to similar ionic activity between Sm^(3+)and Lu^(3+),thus eruptive PLQY of 74.58%in the visible light region and 23.12%in the NIR light region can be obtained.Moreover,Sb^(3+)/Sm^(3+)-codoped Cs_(2)Na Lu Cl_(6)exhibits tunable emission characteristic in the visible light region under different excitation wavelengths,which can change from blue emission(254 nm excitation)to white emission(365 nm excitation).More particularly,only the NIR emission can be captured by the NIR camera when a 700 nm cutoff filter is added.The excellent stability and unique optical properties of Sb^(3+)/Sm^(3+)-codoped Cs_(2)Na Lu Cl_(6)enable us to demonstrate its applications in NIR light-emitting diode,triple-mode fluorescence anti-counterfeiting and information encryption.These findings provide new inspiration for the application of rare earth-based double perovskite in optoelectronic devices.展开更多
Indium(In)-based halide perovskites are desirable for next-generation phosphors and emitting devices,due to their broad emission,nontoxicity,and oxidization avoidance capabilities.However,the In-based perovskites alwa...Indium(In)-based halide perovskites are desirable for next-generation phosphors and emitting devices,due to their broad emission,nontoxicity,and oxidization avoidance capabilities.However,the In-based perovskites always exhibit low external photoluminescence quantum efficiency(PLQE)as a result of their weak light absorption near the corresponding excitation region,and thus,are limited in extended applications.Herein,we have developed an antimony(Sb)-doping strategy to improve the absorption ability of Cs2InCl5·H2O in the ultraviolet region.Excitingly,we obtained a warm-light phosphor with ultrahigh external(internal)PLQE of 72.8%(86.7%).Typically,upon 1.5%Sb doping,the single-crystalline Cs2InCl5·H2O perovskite displayed a stronger warm-light emission at∼610 nm with a large Stokes shift of 295 nm and full width at half maximum(FWHM)of 164 nm.Density functional theory(DFT)calculations revealed that the Sb-doping induced an impurity level in the bandgap,increasing the density of state(DOS),and promoted more carriers into the conduction band maximum.Furthermore,external PLQE from 18%to 59%could be realized in other zero-dimensional In-based perovskites through the same doping strategy.展开更多
Ion doping has been demonstrated as a practical approach to achieving highly efficient luminescence in both inorganic phosphors and organic-inorganic hybrids.The asformed doping species show great potential in optoele...Ion doping has been demonstrated as a practical approach to achieving highly efficient luminescence in both inorganic phosphors and organic-inorganic hybrids.The asformed doping species show great potential in optoelectronic applications due to their high photoluminescence quantum yield(PLQY)and excellent stability.Herein,we report highly emissive Sb^(3+)-doped indium halides(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb(C_(6)H_(18)N_(2)^(2+)=N,N,N',N'-tetramethylethane-1,2-diammonium)prepared by solution evaporation methods with an emission that peaked at 565 nm and a PLQY of 74.6%.Photophysical characterizations and density functional theory computational studies verify the broadband emission originating from a self-trapped exciton.Interestingly,a drastic red shift of the emission peak from 565 to 663 nm with yellow luminescence turning to red is observed once the(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb hybrid is exposed to methanol vapor.Moreover,when the methanol-exposed hybrid is put in air,the emission reverts to 565 nm in several minutes.Single-crystal X-ray diffraction studies show a subsequent structure distortion upon the coordination of methanol to the Sb(III)center,which is responsible for the drastic red shift of the emission.Encouragingly,we found that(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb exhibits a specific response to methanol vapor after screening a series of volatile organic compounds with different polarities.Besides,a negligible change of the emission intensity is observed after several cycles of uptaking and releasing methanol.The high fatigue resistance and specific solvent response of the Sb^(3+)-doped indium halide make it a very promising methanol detector.展开更多
Based on the framework of the effective-mass approximation, the ionized acceptor bound exciton （A- X） binding energy and the emission wavelength are investigated for a cylindrical wurtzite （WZ） GaN/A1x Ga1-xN quan...Based on the framework of the effective-mass approximation, the ionized acceptor bound exciton （A- X） binding energy and the emission wavelength are investigated for a cylindrical wurtzite （WZ） GaN/A1x Ga1-xN quantum dot （QD） with finite potential barriers by means of a variational method. Numerical results show that the binding energy and the emission wavelength highly depend on the QD size, the position of the ionized acceptor and the Al composition x of the barrier material AIxGal-xN. The binding energy and the emission wavelength are larger when the acceptor is located in the vicinity of the left interface of the QD. In particular, the binding energy of （ A-, X） complex is insensitive to the dot height when the acceptor is located at the left boundary of the QD. The ionized acceptor bound exciton binding energy and the emission wavelength are both increased if Al composition x is increased.展开更多
Perovskite variants have attracted wide interest because of the lead-free nature and strong self-trapped exciton (STE) emission. Divalent Sn(II) in CsSnX3 perovskites is easily oxidized to tetravalent Sn(IV), and the ...Perovskite variants have attracted wide interest because of the lead-free nature and strong self-trapped exciton (STE) emission. Divalent Sn(II) in CsSnX3 perovskites is easily oxidized to tetravalent Sn(IV), and the resulted Cs2SnCl6 vacancy-ordered perovskite variant exhibits poor photoluminescence property although it has a direct band gap. Controllable doping is an effective strategy to regulate the optical properties of Cs2SnX6. Herein, combining the first principles calculation and spectral analysis, we attempted to understand the luminescence mechanism of Te4+-doped Cs2SnCl6 lead-free perovskite variants. The chemical potential and defect formation energy are calculated to confirm theoretically the feasible substitutability of tetravalent Te4+ ions in Cs2SnCl6 lattices for the Sn-site. Through analysis of the absorption, emission/excitation, and time-resolved photoluminescence (PL) spectroscopy, the intense green-yellow emission in Te4+:Cs2SnCl6 was considered to originate from the triplet Te(IV) ion 3P1→1S0 STE recombination. Temperature-dependent PL spectra demonstrated the strong electron-phonon coupling that inducing an evident lattice distortion to produce STEs. We further calculated the electronic band structure and molecular orbital levels to reveal the underlying photophysical process. These results will shed light on the doping modulated luminescence properties in stable lead-free Cs2MX6 vacancy-ordered perovskite variants and be helpful to understand the optical properties and physical processes of doped perovskite variants.展开更多
基金support from the National Key R&D Program of China(No.2022YFB2803900)the National Natural Science Foundation of China(Nos.12074347,12004346,12204426,and 61935009)+1 种基金Science Foundation for Distinguished Young Scholars of Henan Province(No.212300410019)the Support Program for Scientific and Technological Innovation Teams of Higher Education in Henan Province(No.231RTSTHN012).
文摘The vacancy-ordered quadruple perovskite Cs_(4)CdBi_(2)Cl_(12),as a newly-emerging lead-free perovskite system,has attracted great research interest due to its excellent stability and direct band gap.However,the poor luminescence performance limits its application in light-emitting diodes(LEDs)and other fields.Herein,for the first time,an Ag^(+)ion doping strategy was proposed to greatly improve the emission performance of Cs_(4)CdBi_(2)Cl_(12) synthesized by hydrothermal method.Density functional theory calculations combined with experimental results evidence that the weak orange emission from Cs_(4)CdBi_(2)Cl_(12) is attributed to the phonon scattering and energy level crossing due to the large lattice distortion under excited states.Fortunately,Ag^(+)ion doping breaks the intrinsic crystal field environment of Cs_(4)CdBi_(2)Cl_(12),suppresses the crossover between ground and excited states,and reduces the energy loss in the form of nonradiative recombination.At a critical doping amount of 0.8%,the emission intensity of Cs_(4)CdBi_(2)Cl_(12):Ag^(+)reaches the maximum,about eight times that of the pristine sample.Moreover,the doped Cs_(4)CdBi_(2)Cl_(12) still maintains excellent stability against heat,ultraviolet irradiation,and environmental oxygen/moisture.The above advantages make it possible for this material to be used as solid-state phosphors for white LEDs applications,and the Commission International de I’Eclairage color coordinates of(0.31,0.34)and high color rendering index of 90.6 were achieved.More importantly,the white LED demonstrates remarkable operation stability in air ambient,showing almost no emission decay after a long working time for 48 h.We believe that this study puts forward an effective ion-doping strategy for emission enhancement of vacancy-ordered quadruple perovskite Cs_(4)CdBi_(2)Cl_(12),highlighting its great potential as efficient emitter compatible for practical applications.
基金Scientific and Technological Bases and Talents of Guangxi(Nos.Guike AD23026119,AD21238027)the Guangxi National Science Fundation Project(No.2020GXNSFDA238004)the“Guangxi Bagui Scholars”foundation for financial support。
文摘Rare earth ions(RE^(3+))-doped double perovskites have attracted tremendous attention for its fascinating optical properties.Nevertheless,RE^(3+)generally exhibits poor photoluminescence quantum yield(PLQY)for their parity-forbidden 4f-4f transition and the low doping concentration.Herein,we reported Sb^(3+)/Sm^(3+)-codoped rare earth-based double perovskite Cs_(2)Na Lu Cl_(6)that enables efficient visible and nearinfrared(NIR)emission,which stems from self-trapped exciton(STE)and Sm^(3+),respectively.Benefit from up to 72.89%energy transfer efficiency from STE to Sm^(3+)and high doping concentrations due to similar ionic activity between Sm^(3+)and Lu^(3+),thus eruptive PLQY of 74.58%in the visible light region and 23.12%in the NIR light region can be obtained.Moreover,Sb^(3+)/Sm^(3+)-codoped Cs_(2)Na Lu Cl_(6)exhibits tunable emission characteristic in the visible light region under different excitation wavelengths,which can change from blue emission(254 nm excitation)to white emission(365 nm excitation).More particularly,only the NIR emission can be captured by the NIR camera when a 700 nm cutoff filter is added.The excellent stability and unique optical properties of Sb^(3+)/Sm^(3+)-codoped Cs_(2)Na Lu Cl_(6)enable us to demonstrate its applications in NIR light-emitting diode,triple-mode fluorescence anti-counterfeiting and information encryption.These findings provide new inspiration for the application of rare earth-based double perovskite in optoelectronic devices.
基金the National Natural Science Foundation of China(grant no.21821004 and 21673005)the Ministry of Science and Technology of China(973 project grant no.2014CB239303).
文摘Indium(In)-based halide perovskites are desirable for next-generation phosphors and emitting devices,due to their broad emission,nontoxicity,and oxidization avoidance capabilities.However,the In-based perovskites always exhibit low external photoluminescence quantum efficiency(PLQE)as a result of their weak light absorption near the corresponding excitation region,and thus,are limited in extended applications.Herein,we have developed an antimony(Sb)-doping strategy to improve the absorption ability of Cs2InCl5·H2O in the ultraviolet region.Excitingly,we obtained a warm-light phosphor with ultrahigh external(internal)PLQE of 72.8%(86.7%).Typically,upon 1.5%Sb doping,the single-crystalline Cs2InCl5·H2O perovskite displayed a stronger warm-light emission at∼610 nm with a large Stokes shift of 295 nm and full width at half maximum(FWHM)of 164 nm.Density functional theory(DFT)calculations revealed that the Sb-doping induced an impurity level in the bandgap,increasing the density of state(DOS),and promoted more carriers into the conduction band maximum.Furthermore,external PLQE from 18%to 59%could be realized in other zero-dimensional In-based perovskites through the same doping strategy.
基金supported by the National Natural Science Foundation of China(22175181,92061202,and 21531008)Fujian Science and Technology Project(2020L3022)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB20000000)。
文摘Ion doping has been demonstrated as a practical approach to achieving highly efficient luminescence in both inorganic phosphors and organic-inorganic hybrids.The asformed doping species show great potential in optoelectronic applications due to their high photoluminescence quantum yield(PLQY)and excellent stability.Herein,we report highly emissive Sb^(3+)-doped indium halides(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb(C_(6)H_(18)N_(2)^(2+)=N,N,N',N'-tetramethylethane-1,2-diammonium)prepared by solution evaporation methods with an emission that peaked at 565 nm and a PLQY of 74.6%.Photophysical characterizations and density functional theory computational studies verify the broadband emission originating from a self-trapped exciton.Interestingly,a drastic red shift of the emission peak from 565 to 663 nm with yellow luminescence turning to red is observed once the(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb hybrid is exposed to methanol vapor.Moreover,when the methanol-exposed hybrid is put in air,the emission reverts to 565 nm in several minutes.Single-crystal X-ray diffraction studies show a subsequent structure distortion upon the coordination of methanol to the Sb(III)center,which is responsible for the drastic red shift of the emission.Encouragingly,we found that(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb exhibits a specific response to methanol vapor after screening a series of volatile organic compounds with different polarities.Besides,a negligible change of the emission intensity is observed after several cycles of uptaking and releasing methanol.The high fatigue resistance and specific solvent response of the Sb^(3+)-doped indium halide make it a very promising methanol detector.
基金Supported by Technology Projects of the Education Bureau of Fujian Province umder Grant No. JK2009038
文摘Based on the framework of the effective-mass approximation, the ionized acceptor bound exciton （A- X） binding energy and the emission wavelength are investigated for a cylindrical wurtzite （WZ） GaN/A1x Ga1-xN quantum dot （QD） with finite potential barriers by means of a variational method. Numerical results show that the binding energy and the emission wavelength highly depend on the QD size, the position of the ionized acceptor and the Al composition x of the barrier material AIxGal-xN. The binding energy and the emission wavelength are larger when the acceptor is located in the vicinity of the left interface of the QD. In particular, the binding energy of （ A-, X） complex is insensitive to the dot height when the acceptor is located at the left boundary of the QD. The ionized acceptor bound exciton binding energy and the emission wavelength are both increased if Al composition x is increased.
基金This work was supported by the National Natural Science Foundation of China(Nos.21661010 and 11774134)Guangxi Natural Science Foundation(No.2017GXNSFGA198005)+1 种基金Natural Science Foundation of Hunan Province(No.2020JJ4424)Research Foundation of Education Bureau of Hunan Province(No.18A009)。
文摘Perovskite variants have attracted wide interest because of the lead-free nature and strong self-trapped exciton (STE) emission. Divalent Sn(II) in CsSnX3 perovskites is easily oxidized to tetravalent Sn(IV), and the resulted Cs2SnCl6 vacancy-ordered perovskite variant exhibits poor photoluminescence property although it has a direct band gap. Controllable doping is an effective strategy to regulate the optical properties of Cs2SnX6. Herein, combining the first principles calculation and spectral analysis, we attempted to understand the luminescence mechanism of Te4+-doped Cs2SnCl6 lead-free perovskite variants. The chemical potential and defect formation energy are calculated to confirm theoretically the feasible substitutability of tetravalent Te4+ ions in Cs2SnCl6 lattices for the Sn-site. Through analysis of the absorption, emission/excitation, and time-resolved photoluminescence (PL) spectroscopy, the intense green-yellow emission in Te4+:Cs2SnCl6 was considered to originate from the triplet Te(IV) ion 3P1→1S0 STE recombination. Temperature-dependent PL spectra demonstrated the strong electron-phonon coupling that inducing an evident lattice distortion to produce STEs. We further calculated the electronic band structure and molecular orbital levels to reveal the underlying photophysical process. These results will shed light on the doping modulated luminescence properties in stable lead-free Cs2MX6 vacancy-ordered perovskite variants and be helpful to understand the optical properties and physical processes of doped perovskite variants.
