Synthesis And Luminescence Tuning Of Rare-earth-doped Nitride Materials

Rare-earth-doped nitride phosphors possess several advantages such as excellent physical and chemical stability,efficient luminescence efficiency and outstanding luminescence thermal stability.This paper mainly explores the photoluminescence and persistent luminescence(PersL)properties of rare-earthdoped nitride phosphors.Through exploring the PersL mechanism and the calculation method of trap energy level,the composition and structure of the phosphor can be designed,which contribute to adjusting the PersL performance.Besides,Yb3+-doped nitride phosphor with low-energy charge transfer band and near-infrared emission is developed to meet the needs in different application fields.The main research results are as follows:(1)An improved peak position method for calculating trap level is proposed.Through theoretical derivation and numerical analysis,the trap level calculation formula including the heating rate β is obtained.Compared with the traditional peak position method Tm/500,the improved peak position method further improves the accuracy of the peak position method on the basis of its simplicity and versatility.(2)The PersL and photostimulated luminescence properties of red nitride phosphor SrLiAl3N4:Eu2+are studied.The analysis of thermoluminescence spectra show that the PersL mainly originates from the shallow traps(0.47 eV),and the photostimulated luminescence mainly originates from the deep traps(0.81 eV).Through analyzing the thermoluminescence excitation spectra and constructing the electronic structure diagram,the mechanism of PersL and photostimulated luminescence is elucidated.The DFT calculation suggests that the traps originate from nitrogen vacancies.The PersL property is regulated by bandgap engineering and trap engineering,and the persistent duration is prolonged by co-doping Tm3+ion.(3)The yellow PersL nitride phosphor SrYSi4N7:Eu2+is synthesized and the effect of Eu2+doping concentration on the PersL performance is studied systematically.The optimal doping concentration of Eu2-is 0.1%.The PersL mechanism of the phosphor is elucidated by measuring thermoluminescence curves,and the PersL performance is regulated by trap engineering.(4)A near-infrared nitride phosphor La3Si6N11:Yb3+with low-energy charge transfer band is designed and synthesized.The optimal content of Yb3+is 2%and the excitation wavelength covers 250-500 nm.The emission peak is located at 983 nm with the full width at half maximum of 13 nm.The phosphor has the excellent luminescence thermal stability with the thermal quenching temperature of about 470 K.The electronic structure diagram of the material is constructed.The nearinfrared pc-LED device is fabricated by combining this phosphor with ultraviolet LED chip,and the potential application of this device is demonstrated.