Study On Preparation And Luminescent Properties Of Silicate/Molybdate Phosphors For White LED

With the development of science and technology,human demand for energy has been increasing,which lead to several energy crisis.Energy conservation and emission reduction are urgent problems to be solved.The lighting sector consumes about 11% of the country's gross generation in China.White LEDs have been widely studied for their energy saving,long life,high luminous efficiency,and low mercury-free toxicity,which provided technical support to solve the problem of energy saving in the lighting sector.At present,the mainstream implementation of white LEDs is the phosphor conversion method,which is lower in cost and simpler in process than others.The stability and luminescence properties of phosphors affect the luminescence properties of white LEDs.The traditional blue-chip-excited YAG:Ce³⁺phosphors have low color rendering index due to the lack of red emission.Therefore,The development of trichromatic phosphors that can be excited by blue or UV has become a frontier topic and an important target of luminescent materials.In this thesis,Li2SrSiO4 and Li2CaSiO4 host were used as the research project,and Ce³⁺and Eu²⁺were used as doped ions to prepare silicate phosphors which could be excited by UV.SrMoO₄:Eu³⁺phosphors were synthesized,which can be excited by blue light to produce red light.It can be co-coated with YAG:Ce³⁺phosphor on the blue chip to make up for the lack of red emission,which can enhance the color rendering index.In this thesis,the phosphors were synthesized by high temperature solid-state method,and the crystal structure and photoluminescence spectrum were analyzed.The crystals were determined to be pure samples by crystal structure analysis.The excitation and emission wavelengths of the phosphor and the optimum doping concentration of the rare-earth ions were determined by analysis of the photoluminescence spectrum.The research contents of this thesis are as follows:1.The luminescence properties of Li₂SrSiO₄:Eu²⁺:This phosphor can be excited at 400nm.The emission wavelength is 564 nm.The optimum doping concentration of Eu²⁺is 0.75 mol%,and the CIE was calculated to be?0.472,0.5522?.2.The luminescence properties of Li₂SrSiO₄:Ce³⁺:This phosphor can be excited at 363 nm.The emission wavelength is 403 nm.the optimal doping concentration of Ce³⁺was 1.0 mol%.3.The luminescence properties of Li₂CaSiO₄:Eu²⁺:This phosphor can be excited at NUV?285nm,378 nm?.The optimum doping concentration of Eu²⁺is 1.0 mol%.The emission wavelength is 482 nm,and the CIE was calculated to be?0.1541,0.2478?.4.The luminescence properties of Li₂CaSiO₄:Ce³⁺:The phosphor can be excited by 272 nm light.The emission wavelength is 377 nm and 404 nm,and the optimal doping concentration of Ce³⁺is 0.8 mol%.5.The luminescence properties of SrMoO₄:Eu³⁺:The phosphor can be excited by 464 nm light,and the emission wavelength is 615 nm,and the optimum concentration of Eu3+is 30.0 mol%.The effects of charge compensator?Li⁺,Na⁺,K⁺,Cl^-?types and concentrations on the luminescence properties of the phosphors were studied.The addition of Na₂CO₃ can significantly enhance the luminescence intensity.When the addition amount is 9.0 mol%,the luminescence intensity is about 4.7 times than the blank group.