Mn⁴⁺, Cr³⁺ Activated Deep Red And Near-infrared Fluorescent Materials Synthesis And Luminescence Properties

Oxide phosphors have been widely used in color TV,kinescope,computer monitor,high-end security monitoring,medical imaging diagnosis?CT/PET?,energy-saving lighting of semiconductor,efficiency increase of crystalline silicon solar cells for light conversion,nondestructive flaw detection,nuclear physics,military and other fields because of great varieties,stable structure and excellent performance.With the rapid development of lighting and color rendering,new energy industry,the fluorescent material market sticks up a relentless march.In the selection of activators for activating fluorescent materials,the R&D of substitutes for valuable rare earth ions have broad prospects and the non rare earth elements have huge market potential.For example,the transition metal ion Mn₄⁴⁺ is characteristic of low cost,and has tunability of exhibiting different emission wavelengths in different coordination environments.The transition metal ion Cr⁴⁺ is often used as a luminescent central ion in many host crystals,its luminescence is usually located in the red and deep red emission regions and can be applied toefficientspectrumconversion of solar cells.Therefore,it is of great fundamental significance and certain practical value to explore luminescence performance and structure feature of new oxide fluorescentmaterials.In this paper,the preparation of transition metal ions Mn₄⁴⁺,Cr⁴⁺ doped several oxide fluorescent materials and their deep red,near-infrared luminescent properties.were explored.A series of Mn₄⁴⁺ activated SrLaScO₄ and SrLa₂Sc₂O₇ crimson oxide phosphors and Cr⁴⁺ activated Na₂CaSn₂Ge₃O₁₂ near-infrared oxide phosphors were prepared,respectively.The crystal structure,fluorescent property,surface morphology and thermal quenching propety of the prepared fluorescent powders were investigated by X-ray diffraction?XRD?,fluorescence spectrum measurement?PL?,diffuse reflectance spectroscopy and scanning electron microscopy?SEM?,etc.Their potential applications in the field of warm white LED and research on light conversion materials for enhancing efficiency of crystalline silicon solar cells are also discussed.The specific studies are as follows:1.Mn₄⁴⁺ was doped into the matrix of SrLaScO₄ and SrLa₂Sc₂O₇ with advantages of typical K₂NiF₄ structure by high temperature solid-state method,Mn₄⁴⁺ activated narrow band emission crimson phosphor has been obtained.The luminescent properties of SrLaScO₄:Mn₄⁴⁺ and SrLa₂Sc₂O₇:Mn₄⁴⁺ were studied and analyzed for the first time by analyzing their fluorescence excitation,emission spectra and UV-Vis DRS spectrum.Meanwhile,the peak positions of each spectrum were assigned,the broadband excitation peaks which locate at 360 nm and 510 nm correspond to the transitions of Mn₄⁴⁺ from the ground state to the excited state transition of ⁴A₂?⁴T₁ and ⁴A₂?⁴T₂,the emission which locates at 690nm corresponds to the transition of ²E?⁴A₂.The results show that the red emission of SrLaScO₄:Mn₄⁴⁺,SrLa₂Sc₂O₇:Mn₄⁴⁺ represents high color purity by irradiation of 360 nm light,it is a potential new type of deep red fluorescent materials uesd for warm white LED.The emission range of 650-750 nm also satisfies the requirements of the solar cell response spectral band.It can also be applied to solar light conversion materials to achieve the photovoltaic synergistic effect.2.A series of Na₂CaSn₂Ge₃O₁₂:Cr⁴⁺ light trans phosphors with wide-band absorption in the visible region and broad-band emission in the near-infrared region were prepared by the high temperature solid state reaction method,and the crystal structure and luminescence properties of the samples were researched as well.The results indicate that the Cr⁴⁺ substituted Sn4⁴⁺ and occupied the central position of the SnO₆ octahedron.It has a broadband excitation located in 380?780 nm in the germanium stannate matrix material of Na₂CaSn₂Ge₃O₁₂,and the near-infrared emission located in 680?880nm are from ²E?⁴A₂ and ⁴T₂?⁴A₂ transitions of Cr⁴⁺.Therefore,Na₂CaSn₂Ge₃O₁₂:Cr⁴⁺ phosphors have potential applications in solar cells and can be used as a solar spectrum conversion material.