Synthesis Of Fluorescence Enhanced Upconversion Nanofibers NaYF4: Yb, Er And Its Application In Dye Solar Cells

In recent years, NaYF4:Yb,Er, acted as one of the most efficient rare-earth (RE)doped fluoride up-conversion luminescence (UCL) materials, has drawn considerableinterest due to its extensive applications in biological labels, analysis detection,biomedical imaging, solar cells, optical storage, infrared quantum counters,next-generation lighting, and three-dimensional displays. However, the low UCLefficiency of NaYF4:Yb,Er nanocrystals (NCs) limits their widespread and in-depthuse. Meanwhile, the small absorption cross-section of excitation light also limits theefficiency. Therefore, how to improve the efficiency of UCL is a challenging work.Herein, we report two effective ways, surface passivation and δ-doping, to enhancethe UC fluorescence efficiency of NaYF4:Yb,Er UCNPs. All of the prepared sampleswere characterized and explained by TEM, HRTEM, XRD and PL, respectively. Agnanoparticles were also synthesized and mixed with the UCNPs in a percentage inorder to promote the fluorescent yield of UCNPs. Ag/δ-UCNPs films were fabricatedby using the spin-coating method, which were applied in Dye-sensitized solar cell(DSSC) to get the harvesting of photoelectric conversion efficiency.一、 The NaYF4:Yb,Er, NaYF4:Yb,Er@NaYF4and δ-doping NaYF4:Yb,ErUCNPs with high crystallinity, good dispersion and uniform morphology wereprepared by using a high-temperature solution method using LnCl3(Ln: Y, Yb, Er),NH4F and NaOH acted as the precursors. The morphology and size of the UCNPs canbe controled by adjusting the reaction temperature, reaction time and etc. Theas-prepared particles were characterized by TEM, HRTEM, XRD, and PL.二、Ag NPs (40nm) were prepared by using the solvothermal method, whichwere characterized by TEM, HRTEM, XRD, UV-Vis etc. A detailed study to explorethe effect of Ag-plasmon-enhanced up-conversion phosphors, a sample of theβ-NaYF4:Yb,Er or NaYF4:Yb,Er@NaYF4or δ-doping NaYF4:Yb,Er UCNPs wasmixed with different concentrations of Ag nanoparticles respectively. For this studyAg-nanoparticles (40nm in diameter) were mixed with a solution of UC nanoparticlesdispersed into cyclohexane. This result indicated the promise of combiningdelta-doping with the plasmonic enhancement effect to achieve significant gains inup-conversion efficiency.三、UC films of Ag/UCNPs were fabricated and applied in DSSC, the measuredI-V curves showed that the photoelectric conversion efficiency of DSSC increased 38%after introducing theAg/δ-UCNPs films compared with pure DSSC.