First-principles Study On Optical Properties Of Ga/Sb Doped YAG:Ce Phosphors For Laser Display

In recent years,as people's demand for display quality has increased,various display technologies have emerged.Among them,laser display technology,with its unique advantages of wide color gamut,high brightness and high saturation,has attracted the attention of major manufacturers and researchers.Phosphor materials for laser display are the core of laser display technology and getting phosphor powder with excellent fluorescence performance is a major topic for researchers.Ce-doped YAG phosphor has the advantages of being easily excited by blue light,wide emission spectrum,and good high temperature resistance,and is a kind of phosphor widely used in laser display technology.Although the Ce-doped YAG phosphor has good luminescence characteristics and stability,it also has certain problems,such as too long fluorescence lifetime,low quantum yield and insufficient red spectral components,etc.The problem of insufficient red spectral components will lead to low color rendering index of white light,which affects the color rendering performance of the laser display system,and severely limits the use of this phosphor in the field of laser display.The solution currently used is mainly to add other rare earth ions or metal cations to the Ce doped YAG phosphor to change the luminescent properties of the phosphor.Ga and Sb are two commonly used incorporation elements of the phosphor,and are widely used in experimental preparation.However,there are few theoretical studies on the incorporation of these two elements.Therefore,the doping effect of Ga and Sb has been studied using the first-principles calculation method.In this paper,the first-principles method is adopted and the general properties of the phosphor system before and after doping with Ga and Sb are simulated using the generalized gradient functional.Based on the calculation results,the effects of Ga and Sb on the YAG lattice are studied.In this paper,we analyze the properties of Ga-doped YAG phosphor system and Sb-doped YAG phosphor system in two parts.The first-principles calculation method was used to calculate the crystal structure, band structure and absorption spectrum of Ga-doped YAG:Ce phosphor system to analyze the effect of Ga doping.Ga can occupy two different positions of A1 and Y.The two substitution systems have little energy change compared to that before doping,and the structures are stable.In the system that Ga replaces Al,the lattice constant increases;in the system that Ga replaces Y,the lattice constant decreases.The band gaps of the two substitution systems are reduced compared to those before doping,which results in a decrease in the energy required for the transition and a red shift in the absorption spectrum.At the same time,the peak of the absorption spectrum of the Ga-substituted Al system increases,and the peak of the absorption spectrum of the Ga-substituted Y system deincreases.Based on the analysis of the 4f energy level of Ce,we also found that the excitation and emission spectra of the Ga-substituted Al system undergo a blue shift,while the excitation and emission spectra of the Ga-substituted Y system exhibit a red shift.The first-principles calculation method was used to calculate the crystal structure,band structure and absorption spectrum of the Sb-doped YAG:Ce phosphor system.Sb can occupy the Y-site.The substitution system of different doping components has a small change in energy before doping and the structure is stable.After Sb replaced Y into the lattice,the distortion of the lattice due to the incorporation of Ce was repaired,the entire doping system was more stable,and the luminescent properties of the phosphor were improved.The band gaps of the substituted systems of different concentrations are reduced,so that the energy required for the transition is reduced,and the absorption spectrum undergoes a red shift.At the same time,after Sb is incorporated,new impurity levels appear in the bandgap.After Sb incorporation,due to the reduction of bandgap and the generation of impurity levels,the absorption spectrum red-shifts and the intensity of the absorption spectrum increases,and with the increase of the doping components,The intensitys of the redshift amplitude and the absorption spectrum gradually increase.