Investigation On Phosphors Under Blue Light Excitation For White Light Emitting Diodes

Abstract：Today’s commercial pc-WLEDs normally use a blue-LED chip covered byyttrium aluminum garnet yellow phosphor coating (Y₃Al₅O₁₂:Ce, YAG:Ce), whichwas invented by Nichia Chemical Co. However, the WLEDs made by means of bluechip+YAG:Ce have poor color rendering index, due to the shortage of red emission.In order to avoid international patent blockade of blue LED+yellow phosphors andimprove color rendering index, the paper concentrates on yellow phosphorLa4Ca（SiO4）3O and red phosphors Ca4O（PO4）2phosphors excited by blue light andanalyzes the influence of activator concentration on optical properties, adjusts hoststructure to optimize the luminescent properties. And its main technical points asfollows:Sol-gel synthesis of La4Ca（SiO4）3O yellow-emitting phosphors, Crystallinephase was characterized by means of XRD, when the sintering temperature beyond1350℃, doping a small amount of Ce³⁺, Mg²⁺, Sr2+did not have any influence on thestructure. Optical performance was investigated by luminescence spectrum.Concentration quenching occurred obviously when Ce³⁺concentration beyond5mol%. Through doping alkaline metal ion replace Ca2+ion to study the opticalperformance and analyzes the result. When Mg²⁺doping amount was3mol%, amaximum PL intensity was obtained. When Sr²⁺doped in host, red-shift of the centerof emission peaking was observed.Ca4O（PO₄）₂doped with Eu²⁺phosphors was prepared by high temperature solidstate method, its spectrum showed long wavelength emission （the maximum is660nm）. It can be excited efficiently at UV and bule light （350⁵00nm）. Throughinvestigating luminescent properties with respect to the concentrations of Eu²⁺,concentration quenching occurred obviously when Eu²⁺concentration beyond2mol%. According to the theory of concentration quenching, energy transfermechanism between Eu²⁺belongs to electric dipole-dipole interaction. When Sr²⁺doped in host, the emission peaks of the phosphors moved toward longer wavelengthslightly with increasing emission intensity were observed. However...