Novel And The Highly Effective Rare-earth Doped Nano-phosphors And Its Application

In recent years, with the rapid development of nanotechnology, rare-earthnanocrystals show attractive charm in vivo fluorescence detection and solar spectrumconversion, which has become one of the frontier and hot issues of nano-materialsand spectra-physics field. However, because of the small absorption cross section ofrare earth ions, the achievement of upconversion luminescence by two photon andmultiphoton process, and the defects and crystalline of nanocrystals which inevitablyintroduced by the nano-material preparation process, low luminous efficiency isalways the bottleneck problem which should to be solved urgently in practicalapplication. So this work carried out the contrustion of the highly effective rare-earthluminescence nano-material, especially the in-depth exploration of luminescenceenhancement of rare earth nano material based on the metal localized surface plasmoneffect. Furthermore, with the highly effective rare earth nano-phosphors, we preparedrare earth nano-photoconversion layer for the OPV cell application to increase theirradiation stability. The main results were shown as follows:[1] Size-controllable YVO4:Eu3+nano/micro-spheres were prepared(20-1200nm), the research of the size-dependent luminescence and dynamics ofYVO4:Eu3+nano/micro-spheres shows that, with the size decrease, the excitationband become narrow in the red side, and the initial population of5D0/5D1initialpopulation increase, and the tunneling model has carried out to explain.[2] Colloidal YVO4:Eu3+@Ag composites were prepared by the seed growthmethod, the luminescence intensity of Eu3+ions are about an order of magnitudeenhancement. It was found that, after coating Ag, the luminescence decay timeconstants and quantum efficiency of the composites increase, and the Zeta potentialchanges from positive to negative, confirmed that the interface effect is the main mechanism of the fluorescence enhancement and proposed the corresponding physicalmodel. And the similar experimental phenomena observed in YVO4:Yb3+,Er3+@Agcomposites.[3] It’s the first time to propose the idea of improving the stability and efficiencyof organic solar cell by the fluorescence conversion layer. And the YVO4:Bi3+,Eu3+photon energy conversion film were prepared, so that the stability of P3HTphotovoltaic materials increased by3times.[4] Ag/NaYF4:Yb,Er nanocomposites was prepared by the self-assembly method,and upconversion luminescence (UCL)(3-4times) and near-infrared emissionenhancement (5-6times) were observed. By excluding the reflection effect of Ag filmand the study of kinetic process, confirmed that the main fluorescence enhancement isby coupling980nm excitation with surface plasmon resonance of Ag nano-film.[5] Combing with the near field effect of silver film and far field effect of3Dphotonic crystals achieved60times UCL enhancement for the first time, which is themost effective enhancement based on the Ag structure. The reasons of high effectiveUCL enhancement are as follows. First, the porous structure can not only effectivelyreduce the distance between UCL nanoparticles (NPs) and silver NPs, but also inhibitlocal thermal effect leading by the excitation light irradiation. Second, the large-sizeAg NPs is benefit to realize the scattering enhancement.[6] It’s found that Er2O3nano-materials and Ag-SiO2-Er2O3nano-composites realized the effective UC broadband white light emission, which caninhibit the concentration quenching and temperature quenching effect. Compared tothe Er2O3nano-materials, UCL strength of the composites increased significantly,approached to the104. Under1200mW power excitation, the UCL intensity ofAg-SiO2-Er2O3composites is over40times than that in NaYF4: Yb3+,Er3+commercialphosphors. In addition, the photo-and thermal-conductive experiments were used toanalyze the mechanisms of UC broadband emission and UC enhancement，andproposed the corresponding physical model.