Low temperature(77 K)photoluminescence measurements have been performed on different GaAs substrates to evaluate the GaAs crystal quality.Several defect-related luminescence peaks have been observed,including 1.452 eV...Low temperature(77 K)photoluminescence measurements have been performed on different GaAs substrates to evaluate the GaAs crystal quality.Several defect-related luminescence peaks have been observed,including 1.452 eV,1.476 eV,1.326 eV peaks deriving from 78 meV GaAs antisite defects,and 1.372 eV,1.289 eV peaks resulting from As vacancy related defects.Changes in photoluminescence emission intensity and emission energy as a function of temperature and excitation power lead to the identification of the defect states.The luminescence mechanisms of the defect states were studied by photoluminescence spectroscopy and the growth quality of GaAs crystal was evaluated.展开更多
In this work,we design oxygen vacancy-rich BiOBr:Yb^(3+)/Er^(3+)(BYE-OV)ultrathin nanosheets,which can effectively enhance UC luminescence by oxygen vacancy engineering.Density functional theory calculations and UV-Vi...In this work,we design oxygen vacancy-rich BiOBr:Yb^(3+)/Er^(3+)(BYE-OV)ultrathin nanosheets,which can effectively enhance UC luminescence by oxygen vacancy engineering.Density functional theory calculations and UV-Vis-NIR absorption spectra reveal that the existence of oxygen vacancies leads to the formation of an intermediate band(IB)in the bandgap,which can enhance the light absorption ability and promote electron excitation and bandgap transitions(VB→CB,VB→IB and IB→CB),thereby providing the transfer of abundant electrons from the host to Er^(3+)ions.As a result,the emission intensity of green and red is exceptionally enhanced by 6.5 and 12 times respectively via introduced oxygen vacancies.Meanwhile,BYE-OV exhibits superior photocatalytic activity for the degradation of RhB under visible-NIR light irradiation.The enhanced activity can be mainly ascribed to enhanced photoabsorption in the visible-NIR region and improved UC luminescence.This work offers a new strategy for a rational design for enhancing UC luminescence,which has potential for applications in visible-NIR light photocatalysis.展开更多
The white upconversion luminescence （UCL） of upconversion nanoparticles （UCNPs） is mainly made up of the color red, green and blue. Interestingly, the white-light-emitting UCNPs can be obtained via a complex metho...The white upconversion luminescence （UCL） of upconversion nanoparticles （UCNPs） is mainly made up of the color red, green and blue. Interestingly, the white-light-emitting UCNPs can be obtained via a complex method of tridoping lanthanide ions such as Yb^3＋, Er^3＋, and Tm^3＋. We herein report that an excellent white UCL can be obtained from Yb/Tm double-doped ZnO. In this system, the blue and red UCL-emissions around 475 and 652 nm originate from ^1G4→^3H6 and ^1G4→^3F4 transition of Tm^3＋, respectively, and the green one can be attributed to the defect states （oxygen va- cancies） luminescence （DSL） of the ZnO host. Meanwhile, the fine nanostructure of ZnO：Yb/Tm is prepared by adjusting the concentration of OH-. Particularly, the one dimentional pencil-shaped nanorods with high aspect ratio achieve a strong green DSL emission due to the high concentration of oxygen vacancy. The oxygen vacancy defects play an irreplaceable role in affecting the intensities of blue and red UCL by acting as the intermediate state in the energy transfer process. More importantly, we demonstrate that the DSL and UCL can be combined into systems, paving a new road for obtaining the white UCL emission.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.21972103)the National Key Research and Development Program of China(Grant No.2016YFB040183)Research and Development Program of Shanxi Province,China(Grant No.201703D111026)
文摘Low temperature(77 K)photoluminescence measurements have been performed on different GaAs substrates to evaluate the GaAs crystal quality.Several defect-related luminescence peaks have been observed,including 1.452 eV,1.476 eV,1.326 eV peaks deriving from 78 meV GaAs antisite defects,and 1.372 eV,1.289 eV peaks resulting from As vacancy related defects.Changes in photoluminescence emission intensity and emission energy as a function of temperature and excitation power lead to the identification of the defect states.The luminescence mechanisms of the defect states were studied by photoluminescence spectroscopy and the growth quality of GaAs crystal was evaluated.
基金supported by the National Natural Science Foundation of China(No.61975245)the Science and Technology Planning Project of Guangdong Province(No.2017A010103035).
文摘In this work,we design oxygen vacancy-rich BiOBr:Yb^(3+)/Er^(3+)(BYE-OV)ultrathin nanosheets,which can effectively enhance UC luminescence by oxygen vacancy engineering.Density functional theory calculations and UV-Vis-NIR absorption spectra reveal that the existence of oxygen vacancies leads to the formation of an intermediate band(IB)in the bandgap,which can enhance the light absorption ability and promote electron excitation and bandgap transitions(VB→CB,VB→IB and IB→CB),thereby providing the transfer of abundant electrons from the host to Er^(3+)ions.As a result,the emission intensity of green and red is exceptionally enhanced by 6.5 and 12 times respectively via introduced oxygen vacancies.Meanwhile,BYE-OV exhibits superior photocatalytic activity for the degradation of RhB under visible-NIR light irradiation.The enhanced activity can be mainly ascribed to enhanced photoabsorption in the visible-NIR region and improved UC luminescence.This work offers a new strategy for a rational design for enhancing UC luminescence,which has potential for applications in visible-NIR light photocatalysis.
基金supported by the National Natural Science Foundation of China (11374080)
文摘The white upconversion luminescence （UCL） of upconversion nanoparticles （UCNPs） is mainly made up of the color red, green and blue. Interestingly, the white-light-emitting UCNPs can be obtained via a complex method of tridoping lanthanide ions such as Yb^3＋, Er^3＋, and Tm^3＋. We herein report that an excellent white UCL can be obtained from Yb/Tm double-doped ZnO. In this system, the blue and red UCL-emissions around 475 and 652 nm originate from ^1G4→^3H6 and ^1G4→^3F4 transition of Tm^3＋, respectively, and the green one can be attributed to the defect states （oxygen va- cancies） luminescence （DSL） of the ZnO host. Meanwhile, the fine nanostructure of ZnO：Yb/Tm is prepared by adjusting the concentration of OH-. Particularly, the one dimentional pencil-shaped nanorods with high aspect ratio achieve a strong green DSL emission due to the high concentration of oxygen vacancy. The oxygen vacancy defects play an irreplaceable role in affecting the intensities of blue and red UCL by acting as the intermediate state in the energy transfer process. More importantly, we demonstrate that the DSL and UCL can be combined into systems, paving a new road for obtaining the white UCL emission.
