Preparation And Properties Of Single Matrix Phosphor Activated By Rare Earth Ions For White-light-emitting Diodes

The white light-emittings diodes?w-LEDs?converted by single-matrix white phosphor have become a research hotspot in the field of w-LEDs owing to the high color rendering index,high conversion efficiency,low production cost and moderate color temperature.Since human eyes are not sensitive to UV/near-UV light,the luminous color of w-LED only depends on phosphors.Therefore,the preparation of single-substrate white phosphors with good luminous property is an important work at present.In this dissertation,we prepared several single-matrix white phosphors doped with rare earth ions that can be excited by UV/near-UV by a sol-gel method or a high-temperature solid-state reaction.The photoluminescence properties and luminescence mechanism of prepared phosphors have been measured by X-ray diffraction?XRD?,photoluminescence,field emission scanning electron microscopy?FE-SEM?,fluorescence decay curve,and UV-vis DRS.1.A series of Ba₂LaV₃O₁₁:Ln³⁺(Ln³⁺=Eu³⁺and/or Dy³⁺)phosphors were prepared by a Pechini-type sol-gel method.XRD measurement results showed that the prepared Ba₂LaV₃O₁₁:Ln³⁺(Ln³⁺=Eu³⁺and/or Dy³⁺)series phosphors are single pure phases,and the doping rare earth ions do not affect the matrix lattice.Under the excitation of UV light at 276 nm,the Ba₂LaV₃O₁₁1 host lattice present a blue-green light,corresponding to a broad band peaking at 498 nm(V⁵⁺-O^2-charge transfer band);Ba₂LaV₃O₁₁:Eu³⁺phosphors emit an orange-red light,corresponding to a broad band peaking at 498 nm(V⁵⁺-O^2-charge transfer band)and the characteristic emission bands of Eu³⁺peaking at 595 nm?⁵D₀-⁷F₁?and 615 nm?⁵D₀-⁷F₂?;the emission spectrum of Ba₂LaV₃O₁₁:Dy³⁺phosphor powder are narrow bands at 486 nm(⁴F_9/2-⁶H_15/2)and 577 nm(⁴F_9/2-⁶H_13/2),showing cold white light emission;For Ba₂LaV₃O₁₁:Dy³⁺,Eu³⁺,the characteristic red light of Eu³⁺can combine with cool-white light of Dy³⁺to obtain high-quality white light.2.A series of Gd₂P₄O₁₃:Ln³⁺(Ln³⁺=Tb³⁺and/or Eu³⁺)phosphors were synthesized by a sol-gel method.XRD and SEM results show that the doping rare earth ions do not affect the matrix lattice.The prepared Gd₂P₄O₁₃:Ln³⁺(Ln³⁺=Tb³⁺and/or Eu³⁺)phosphors are spherical particle with the size of about 500 nm in deameter.Under the excitation of ultraviolet light at 277 nm,The emission spectrum of Gd₂P₄O₁₃:Tb³⁺,Eu³⁺phosphors show the ⁵D₃-⁷F_J?J=6,5,4,3?characteristic emissions and⁵D₄-⁷F_J?J=6,5,4,3?characteristic emissions of Tb³⁺ions?blue-green?and the ⁵D₀-⁷F_J?J=1,2?characteristic emissions of Eu³⁺ions?orange red light?;Due to the energy transfer from Tb³⁺to Eu³⁺in Gd₂P₄O₁₃:Tb³⁺,Eu³⁺phosphors,by changing the doping concentration and relative ratio of Tb³⁺/Eu³⁺ions,the luminescent color of Gd₂P₄O₁₃:Tb³⁺,Eu³⁺phosphors can be tuned from blue light,white light to orange-red light;by precisely adjusting the doping concentration and relative ratio of Eu³⁺and Tb³⁺,we have achieved a single-matrix,high quality white light emission in the Gd₂P₄O₁₃:Tb³⁺,Eu³⁺phosphors.3.A series of Ba₃Y?PO₄?₃:Ln³⁺(Ln³⁺=Tb³⁺,Eu³⁺,Tm³⁺)phosphors were synthesized by a traditional high-temperature solid-state reaction,and its phase formation,luminescence mechanism and energy transfer mechanism were studied in this dissertation.The XRD results show that the Ba₃Y?PO₄?₃:Ln³⁺(Ln³⁺=Tb³⁺,Eu³⁺,Tm³⁺)phosphors are single pure phases.Under the excitation of near-ultraviolet light at 359 nm,the emission spectra of Ba₃Y?PO₄?₃:Ln³⁺(Ln³⁺=Tm³⁺,Tb³⁺,Eu³⁺)phosphors present the characteristic narrow-band emission peaks of Tm³⁺,Tb³⁺,and Eu³⁺,Separate cause:¹D₂-³F₄ characteristic emission of Tb³⁺?blue light?,⁵D₃-⁷F_J?J=6,5,4,3??blue light?and ⁵D₄-⁷F_J?J=6,5,4,3?characteristic emission of Tm³⁺?green light?,⁵D₀-⁷F_J?J=1,2?characteristic emission of Eu³⁺?orange-red light?.Due to the energy transfer between Tb³⁺and Eu³⁺,by changing the doping concentration andrelativeratioofTb³⁺/Eu³⁺/Tm³⁺ions,theluminescentcolorof Ba₃Y?PO₄?₃:Tm³⁺,Tb³⁺,Eu³⁺phosphors can show a green light,yellow light,orange light,white light,blue light,etc.By precisely adjusting the doping concentration and relative ratio of Tm³⁺/Eu³⁺/Tb³⁺,Single-matrix white light emission can be achieved in single-doped and co-doped Ba₃Y?PO₄?₃:Ln³⁺(Ln³⁺=Eu³⁺,Tm³⁺,Tb³⁺)phosphors.