The Spectrum Tuning Of Solid Solution Type （La,Sr）₃Al（O,F）₅:RE³⁺（RE=Ce,Pr,Eu） Phosphor For White LEDs

The phosphor-converted (pc) based white-light-emitting diodes (WLEDs) in solid statelighting (SSL) technology generate white mainly by combining blue InGaN chip with blueexcitable rare earth (RE) ion doped phosphor particulates. For the purpose to improve qualityof emission with low cost, a new compositional phosphor with high quantum efficiency,oxyfluoride-solid solution phosphor, was investigated. Some fundamentals involved in crystalfiled environment of solid solution of phosphor host with tetragonal crystal configuration aswell as its adjustable emission spectrum were detailed. The main achievements that weremade herein were summarized as follows:A. The luminescent properties of Sr2.975-xLaxAlO4+xF1-x:0.025Ce3+(LSAF: Ce3+)phosphors was tuned by varying the composition of solid solutions from two isotopicend-member compounds of Sr3AlO4F and LaSr2AlO5. These phosphors exhibit blue-excitable,strong yellow emission from498nm to553nm. The red-shift of the emission band of LSAF:Ce3+was interpreted from the points of view of both the crystal field effect and theNephelauxetic effect. The temperature dependence of luminescence was observed to begreatly correlated with the incorporation of fluorine ions into the host lattice.B. The effect of Sr2.475La0.5Ce0.025AlO4.5F0.5: y wt%SiO2(LSSAF: Ce3+) on valencestate variation of cerium ion and the enhancement of photoluminescence were investigated.The LSSAF: Ce3+prepared in8%H2/N2condition showed that the luminous intensity of PLwas found to be increase to175%, when the amounts of SiO2added get to be around2.0wt%,ascribed to the addition of SiO2responsible for spontaneous charge compensation to allowfurther reduction of Ce4+to Ce3+.C. Upon co-doping Ce3+, Pr3+and Eu3+ions, energy transfer relation occurs in the hostlattice of a new solid-solution composition of Sr2.975-xLaxAlO4+xF1-x(LSAF) phosphor. Thepathways of energy transfer among Ce3+, Pr3+and Eu3+are proposed to enable red addition tothe primary yellow emission to construct warm white light.D. By applying LSAF:Ce3+phosphor, a InGaN LEDs (450nm) planar lampprototype with remote phosphor was fabricated with printing procedure on glass substrate. Wesimulated light ray trace of this light source to evaluate the illumination and luminousintensity distribution together with experimental measurement. The influence of differentthickness of phosphor layer was observed to be critical to determine the color temperature,color rendering index and luminous efficiency. The parameters we obtained indicate that thephosphor-related interfaces in the transmission route play key roles to achieve the desiredlight-extraction efficiency of the remote phosphor typed lamp.