Surface Plasmon Enhanced Photoluminescence Of Phosphors Doped With Rare Earth Ions For LED

Metallic island films especially of noble metal have attracted much interest for severaldecades due to their unique optical properties and their performance in Metal-enhancedfluorescence （MEF）. More recently, MEF has also been suggested as an effective means toimprove luminous efficiency of light emitting diodes, organic light emitting diodes andphotoluminescence （PL） intensity of single-doped phosphor films or particles. And theexperimental results have been amazing. However, little is known about the MEF ofco-activated phosphors for the overall enhancement or quenching.This work focuses on the luminous intensity of the phosphors doped rare earth ions withlocalized surface plasmon of silver island films, especially with the morphology of Ag films,and the coupling regime between the Ag and luminous center. The mechanism of the PLenhancement is investigated in terms of the local electro-magnetic field, the decay rate ofrecombination radiation and the relation of energy transfer in between co-activators in thehost of phosphor and Ag SP involved in this enhancement. The main achievements obtainedinclude:A．Ag island films were prepared by sputtering. The morphology of SP were dependenton the sputtering time and thermal processing. Meanwhile, the SP resonance wavelength canbe tuned precisely by changing the sputtering time and the condition of thermal processing, sothat to achieve the blue region which we needed.B．The simultaneous emission of 440 nm-peaked blue and 619 nm-peaked red ofBa₃MgSi₂O₈: Eu²⁺, Mn²⁺was enhanced by the MEF through assembling sliver island filmsfor photosynthetic action spectrum. The dual enhanced emission of PAS could be optimized toa maximum with an annealed 50-nm-thick silver film. A 1.42-fold enhancement of blueemission was resulted from MEF-induced resonant coupling between the LSP of Ag and thephotons of blue emission from Eu²⁺. Sequentially, this enhanced photonic energy of blueemission was transferred to the co-activator of Mn²⁺, leading to a 1.47-fold intensification ofred emission.C．For SrSi₂O₂N₂: Eu²⁺, Mn²⁺, the emission intensity of Ag/SrSi₂O₂N₂: Eu²⁺,Mn²⁺wasexplored. The analysis results showed that the PL intensity was quenched, in which the effectare due to three possible factors. One is that Ag LSP absorbed more excitation energy. Asecond is that the thickness of phosphor layer exceeded the penetration depth of the Ag LSP.The third is no increase in the utilization of the incident light.This paper is indicated that localized field enhancement due to the LSPR of metal islandfilms could improve the emission intensity of phosphor doped with rare earth ions, whichshows potential application in MEF and LED solid state lighting.