Study On Controllable Preparation And Luminescence Properties Of The Broadband Near-infrared Phosphor: ScF₃:Cr³⁺

Near-infrared（NIR）detection technology has the advantages of simple,fast,non-invasive and high-resolution ratio,which plays a significant role in solving food safety problems,healthy diet problems and early detection of tumors.In recent years,scientists have advocated the integration of near-infrared spectroscopy technology into mobile phones,wristbands and other personal portable devices to monitor food nutrients and body status at any time.However,the lack of high-efficiency and miniaturized broadband near infrared light source is the main bottleneck to complete this technology.In numerous technical solutions,phosphor-converted light-emitting diode（pc-LED）has a good application prospect.The technology combines broadband NIR phosphor that can be excited by blue light with the most efficient blue LED chip to obtain high efficiency and miniaturized wideband NIR light source.In this thesis,fluoride ScF₃was used as the matrix material,and excessive metal ion Cr³⁺was used as the activation ion.A series of near-infrared phosphors ScF₃:Cr³⁺,Sc_xGa_1-xF₃:Cr³⁺and Sc_xFe_1-xF₃:Cr³⁺were prepared by hydrothermal method.The controllable synthesis of ScF₃:Cr³⁺was controlled by changing the pH and NH₄F/Sc³⁺and co-doped Ga³⁺and Fe³⁺were used to optimizing properties.Their crystal structure,luminescence properties and applications in near-infrared pc-LED devices were studied and explored.（1）The broadband ScF₃:Cr³⁺phosphor was successfully synthesized by a simple and green hydrothermal method.By controlling pH value and the concentration of the precursor of NH₄F/Sc³⁺,We comfirmed the optimum synthesis conditions of ScF₃:Cr³⁺.The morphology evolution of ScF₃:Cr³⁺phosphor synthesized under different concentrations of pH and NH₄F/Sc³⁺precursor was characterized by SEM.ScF₃:Cr³⁺phosphor presents a broadband emission in the range of 700～1100 nm,with a half peak width of 140 nm and a peak of 853 nm.Compared with room temperature,the emission intensity of ScF₃:Cr³⁺phosphor can maintain 85.5%at 150°C,which is better than many other NIR phosphors reported recently.A NIR pc-LED chip was fabricated on 460 nm blue LED chip.The NIR photoelectric conversion efficiency of the pc-LED device is 3.19%at 40 m A.NIR image acquisition technology was used for night vision imaging of fruits,and the application value of the material is proved.（2）A series of broadband near infrared phosphors Sc_xGa_1-xF₃:Cr³⁺and Sc_xFe_1-xF₃:Cr³⁺were successfully prepared.The effect of Fe³⁺→Cr³⁺energy transfer on the luminescence properties of ScF₃:Cr³⁺phosphors in the negative thermal expansion material system were studied by doping Ga³⁺as the blank control due to the similar ionic radius of Ga³⁺and Fe³⁺ions.The results demonstrate the energy transfer of Fe³⁺→Cr³⁺is helpful to improve the luminescence thermal stability in the negative thermal expansion material ScF₃.Moreover,with the introduction of Ga³⁺and Fe³⁺,the material lattice distortion,the luminescence intensity is enhanced to two times of the original,the maximum internal quantum efficiency can reach 91%,and the FWHM is also increased from 140 nm to 160 nm.Finally,it is fabricated into NIR pc-LED.The near-infrared photoelectric conversion efficiency of the pc-LED device is 10.7%at 20 m A,which is greatly improved compared with the previous work.