| Near-infrared(NIR)long afterglow material is a special material that can absorb energy such as ultraviolet or visible light and can continue to emit NIR light for a period of time after the excitation is stopped.It is used in high-resolution biological imaging,NIR lighting,optical anti-counterfeiting,and high sensitivity.Some imaginative applications have been proposed in the fields of biosensing,high conversion efficiency solar cells,and potential military activities.However,the exploration process of NIR long afterglow materials is still in the preliminary stage.Although in recent years,certain results have been achieved in the research and mechanism exploration of NIR long afterglow materials,the choice of high-cost gallate substrates has largely restricted the luminescence centers available for research.The choice of ion in turn limits the in-depth study of NIR long afterglow materials.Based on this,this thesis focuses on the development of new long-lasting luminescent materials,the exploration of the mechanism of long-lasting,the improvement of luminescence performance and its application in NIR optical communication.The main research contents and results are as follows:(1)A new type of NIR long afterglow material Sr Al12O19:Fe3+activated by Fe3+ions was designed and synthesized by high-temperature solid-phase method.Under the excitation of ultraviolet light,the NIR long afterglow emission,which is located in the 700-1000 nm band and the strongest emission peak is at 811 nm,is attributed to the 4T1(4G)?6A1(6S)transition of Fe3+ions.In order to explore its possible afterglow mechanism.we used fluorescence spectroscopy,thermo-luminescence and EPR measurement methods to do a detailed study on Sr Al12O19:Fe3+phosphors.Experiments show that Sr Al12O19:Fe3+has the typical fluorescence characteristics of Fe3+,and the material has long afterglow emission.The afterglow spectrum is similar to the fluorescence spectrum,and the afterglow time exceeds 2hours.The results of EPR spectroscopy confirmed that the trap corresponding to the EPR signal with g=5.62 played an important role in the afterglow process.Comparing the EPR change of Sr CO3,Al2O3 raw material before and after heating indicates,it shows that the defects in the material are Al-related defects.Through the reduction of Sr Al12O19:Fe3+,and the comparison of the EPR and pyro-release spectra of the reduced and re-oxidized samples,it was confirmed that this signal originated from Al vacancy defects.In this paper,we propose the afterglow mechanism model of long afterglow excitation in Sr Al12O19:Fe3+material,electrons transfer from O2-to Al vacancy defects.(2)NIR long afterglow materials of Sr Al12O19:Fe3+,Mg2+,Ti4+were synthesized by high-temperature solid-phase method.The phase structure analysis of X-ray diffractometer showed that the doping of Fe3+,Mg2+,Ti4+ions did not change the crystal structure of Sr A12O19.The fluorescence spectrum shows that the light at 750-1050 nm is attributed to the 4T1(4G)?6A1(6S)transition of Fe3+ions.The afterglow strength test shows that the afterglow initial strength of the Sr Al12O19:Fe3+,Mg2+,Ti4+material is 100 times that of the Sr Al12O19:Fe3+material,and the afterglow time is also extended to 5 hours.At the same time,we also found that Sr Al12O19:Fe3+,Mg2+,Ti4+materials have spectral response characteristics.Under the excitation of visible light to NIR light,the luminous intensity of the synthesized material is enhanced,indicating that the material has a broadband spectral response capability.In addition,the test results of the spectral response characteristics show that the Sr Al12O19:Fe3+,Mg2+,Ti4+mediated pc-LED can sense external incident light signals of different wavelengths,and can convert the LED signal into a luminescent signal and correlate it with the sensing,So as to achieve multi-functional integration.The intelligent response function of this multi-spectral excitation makes it have huge application potential in optoelectronic devices. |
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