Localized Surface Plasmon Resonance Enhanced Light Emission From Led Phosphors With High Efficiency

White light emitting diode (LED) has attracted increasing attention as a light source for the next-generation general illumination and the automotive lighting applications due to the energy savings and positive environmental effects. In the phosphor conversion approach, phosphor has such a great influence on LED that it is an important task to improve the luminescence efficiency of phosphor. It is an innovation to improve the luminescence efficiency of phosphor with the utilization of localized surface plasmon resonance (LSPR).The ionosphere and metals are both examples of plasmas:media that possess freely mobile charges. Plasmons are resonant modes that involve the interaction between free charges and light. Structuring the metal changes the nature of the plasmonic response of the metal and can allow light to couple to the associated plasmon mode. The plasmon mode supported by metal nanoparticle is known as LSPR. Particle size and shape play an important role in determining the position of the resonance. It may improve the luminescence efficiency of phosphor by coupling the emission light with localized surface plasmon oscillation of metal nanoparticle. We select Ag as the plasma because Ag has the strongest plasmonic interaction with light among all metals.In this paper, CaTiO3:Eu3+red phosphors were coated with Ag through the heterogeneous nucleation and growth of Ag. The samples were characterized by field emission scanning electron microscope (FE-SEM) and fluorescence spectrophotometer (PL). The FE-SEM images showed the importance of the reaction temperature, ammonium hydroxide dropwise addition rate and concentration of AgNO3to the morphology. However, the luminescence efficiency of phosphor hasn’t been improved due to the nonuniform morphology.Therefore, we synthesized Ag nanoparticles with uniform morphology and tunable LSPR, then combined them with CaTiO3:Eu3+red phosphors. In this reaction, H2O2helped to induce the formation of planar twinned seeds while removing possible nontwinned particles, and the polymeric capping agents (PVP and TSC) had the selective adhesion to Ag (111) facets. The samples were characterized by transmission electron microscope (TEM), UV-visible spectrophotometer (UV-Vis). The TEM images revealed that the uniform Ag nanoplates with30-60nm length and about6nm thickness were obtained. By controling the concentration of NaBH4we can tune the surface plasmon band of these Ag nanoplates ranging from462to854nm. This kind of Ag nanoplates can also be obtained without adding PVP.The surface of CaTiO3:Eu3+red phosphors can absorb the Ag nanoplates because of the electrostatic attraction. For a uniform absorption, we use micro injection method to mix them. The phosphors with Ag were characterized by U V-vis, FE-SEM and PL. The extinction spectra and FE-SEM images showed that the Ag nanoplates were absorbed to the surface of CaTiO3:Eu3+red phosphors successfully. Ag nanoplates can enhance or quench the emission intensity of phosphor by matching the emission spectra and LSPR position. Ag nanoplates having a LSPR peak at640nm enabled the enhancement of the red emission intensity. On the contrary, a decrease of the red emissions was attributed to the quenching effect due to the absorption of Ag nanoplates whose LSPR position was not matched. The enhancement rate was increased as the concentration of the Ag nanoplates increased, until it reached the maximum value,25.5%.