Preparation And Photoluminescence Properties Of Eu²⁺,Eu²⁺/Mn²⁺ Doped Ba_0.75Al₁₁O_17.25 Phosphor For Full-spectrum White Light-emitting Diodes

Full-spectrum white light-emitting diodes（WLEDs）have an emission spectrum similar to sunlight and are becoming the mainstream direction of semiconductor lighting technology in the future.Full-spectrum lighting requires WLED color rendering index greater than 90,no high-energy blue light hazard,and no obvious missing parts of the spectrum.The widely used WLEDs are made of blue（460 nm）LED chips with YAG yellow phosphors and nitride red phosphors.This kind of WLEDs is difficult to meet the needs of full-spectrum lighting.In order to improve the light quality of WLEDs,the use of（N）UV（365 nm or 390 nm）LED chips with red,green and blue phosphors has attracted widespread attention.At this stage,the two major factors that limit the development of（N）UV-excited WLEDs are:there are fewer types of blue phosphors that can be efficiently excited by（N）UV,and red,green,and blue phosphors will undergo reabsorption.Therefore,it is necessary to develop new blue phosphors and single-matrix color-tunable phosphors to meet the needs of full-spectrum WLEDs.In this thesis,Ba_0.75Al₁₁O_17.25:Eu²⁺blue phosphor and Ba_0.75Al₁₁O_17.25:Eu²⁺/Mn²⁺color tunable phosphors were synthesized by a solid state method,and they were systematically studied.The main work of this paper is as follows:（1）A series of Eu²⁺doped Ba_0.75Al₁₁O_17.25（BAO）blue phosphors were synthesized by a solid state method,and Li Cl was added as flux to reduce the synthesis temperature.XRD test and Rietveld refinement were used to analyze the BAO matrix crystal structure.The microscopic morphology of the SEM observation is that of fine flakes with a large size range.The Eu²⁺doping concentration was adjusted to obtain the best emission,and the concentration quenching mechanism of this blue phosphor was studied in detail.Li Cl can redshift the excitation peak from 330 nm to 370 nm.The emission intensity of this blue phosphor remains basically unchanged at 150°C,and exhibits excellent photoluminescence thermal stability.By coating BAO:Eu²⁺blue phosphor withβ-Sialon（green）、YAG:Ce³⁺（yellow）and Ca Al Si N₃:Eu²⁺（red）phosphors on a 365 nm LED chip,we obtain a full-spectrum WLED with a color rendering index of 93.4,a correlated color temperature of 4786 K,and a lumen efficiency of 43.33 lm/W.The application potential of this kind of blue phosphor in the field of full-spectrum lighting is confirmed.（2）A series of Eu²⁺/Mn²⁺co-doped BAO color tunable phosphors were synthesized by a solid state method.XRD results show that the synthesized samples are all pure phases.By studying its spectral characteristics,we can change the Mn²⁺ion doping concentration to achieve color regulation from blue to green light.The excitation spectrum of Mn²⁺ion and the emission spectrum of Eu²⁺ion can overlap very well.There is energy transfer between the two ions and we have studied its energy transfer mechanism.The thermal stability test results show that BAO:Eu²⁺/Mn²⁺have excellent photoluminescence thermal stability,and temperature rise will increase the energy transfer efficiency between Eu²⁺and Mn²⁺.Finally,we use this kind of phosphor mixed with YAG:Ce³⁺（yellow）and Ca Al Si N₃:Eu²⁺（red）phosphors to coat on 365 nm LED chip to obtain a full-spectrum WLED with a color rendering index of 90.9,a correlated color temperature of 2782 K,and a lumen efficiency of 45.4 lm/W,which confirms the application potential of this kind of color tunable phosphors in the field of full-spectrum lighting.