Synthesis And Optical Spectroscopy Research Of Rare Earth Doped Phosphor For White LED

This paper mainly discussed preparation and optical properties of rare-earth ions doped phosphors for white LED materials, Including the use of high-temperature solid-phase synthesis for RE (RE = Ce³⁺, Eu²⁺, Tb³⁺) doped Ca₂BO₃Cl phosphors, red emission phosphors of SrLaAlO₄:Eu²⁺, and Eu²⁺-doped Na1-xAl1-xSi1+xO4. And those phosphors have been characterized by XRD, PL, TEM, FESEM and UV-Vis. The main conclusions are as following:The Ca₂BO₃Cl coactivated with Ce³⁺ and Eu²⁺ shows intense UV region absorption and two emission bands: the one at 416 nm is attributed to Ce³⁺, and the other at 570 nm is assigned to Eu²⁺. The spectroscopic data indicates that the Ce³⁺→Eu²⁺ energy transfer process takes place in the host matrix of Ca₂BO₃Cl. The maximum energy transfer efficiency ?T from Ce³⁺ to Eu²⁺ is calculated to be about 84% for Ca₂BO₃Cl:0.03Ce³⁺, 0.03Eu²⁺. Furthermore, we have also demonstrated that the Ca1.97BO3Cl:0.03Ce³⁺,xEu²⁺can be systematically tuned to generate light from cold white, white to warm white light under ultraviolet radiation, which are more numerous than single-emitting YAG:Ce. It has been shown the potential to act as a white-emitting phosphor for ultraviolet LEDs. The red phosphors SrLaAlO₄:Eu²⁺ shows a broad absorption from 420 to 530 nm and has a strong orange-red emission (λem = 605 nm) under the blue excitation of 445 nm. By exciting at different wavelengths (254 and 445 nm), the emission bands change from a broad band excited by 445 nm to sharp lines excited by 254 nm, which can be can be attributed to Eu²⁺ substitution of Sr²⁺ and the Eu³⁺ substitution of La³⁺ in SrLaAlO₄ phosphors, respectively. The optimized sample, SrLaAlO₄:0.03Eu²⁺, show the maximum intensity emission at 605 nm. The CIE chromaticity coordinates for SrLaAlO₄:0.03Eu²⁺ is (0.60, 0.39), which can be used to compensate the red color deficiency of YAG:Ce³⁺-based white LEDs or to create white light by combining with a blue LED chip and another green phosphor.The luminescence of the Na1-xAl1-xSi1+xO4:Eu²⁺ phosphor is characterized by the two corresponding emission centers, namely, Eu1 and Eu2 sites, which peak at 440 and 535 nm, respectively. The Eu²⁺ content 5% and the molar ratio of adding amount of SiO₂ to n=5 present the optimal luminescence characteristics of the material.