Several Novel Rare-earth Doped Energy-conversion Materials And Their Highly Efficient Luminescence Characteristics

In the rare-earth ions doped energy-conversion materials, rare earth ion as a typical isolated luminescence center with unique formation mechanism and application field has attracted more attention. Rare-earth luminescence is the transition between the 4f electrons in the 4f level and 5D level based on the spectrum, which can be observed up to more than thirty thousand. The emission range is from ultraviolet, visible to the infrared of various wavelengths of electromagnetic radiation. The specific electronic energy level structure and 4f electronic shielding effect of rare-earth ion, make the rare-earth luminescent resources become great treasury. Researches on luminescence materials have been concentrated on energy and biological applications rather than energy-efficient lighting solid materials driven by intensified evolution of energy crisis, shortage of natural resources, and environmental pollution etc., and the upcoming nanometer era. In this paper, we synthesis different systems of rare-earth ions doped energy-conversion materials and discuss their photoluminescence characterization.The content of this thesis is as follows:Chapter 1, the species, character and functional application of rare earth ions doped energy-converted materials are introduced. Furthermore, the rare earth ion energy level structure, electric dipole transitions, crystal field effects, energy transfer and other basic physical image are done a simple review, as well as the the background and significance of research content.Chapter 2, the preparation methods of rare earth ions doped energy-converted materials and methods for characterization of the samples are summarized.Chapter 3, down-conversion luminescence and spectral modification based on energy transfer of rare earth ions are explored.First of all, powder samples of Pr3+, Yb3+ co-doped Li2 Te O4 were prepared by solid state synthesis method. Experimental evidences of energy transfer from Pr3+ to Yb3+ were presented by the excitation spectra, emission spectra as well as decay curves at room temperature. From the analysis of temperature-dependent infrared emission spectra, the two possible energy transitions from the Pr3+ to Yb3+ are described as follow:(1) 3P0(Pr3+) â†' 2F5/2(Yb3+) + 2F5/2(Yb3+),(2) 3P0(Pr3+) + 2F7/2(Yb3+) â†' 1G4(Pr3+)+ 2F5/2(Yb3+). The energy transfer from 3P0 level of Pr3+ to Yb3+ was very efficient and the maximum transfer efficiency reached 66.4%.Besides, Ho3+, Yb3+ co-doped Na Y(Mo O4)2 were synthesized by hydrothermal method with well dispersed sample with uniform size(micron). Evidence is provided by spectroscopic measurements to confirm the occurrence of quantum cutting. Upon excitation, near-infrared quantum cutting could occur through a two-step resonance energy transfer from Ho3+ to Yb3+ by cross relaxation.Thirdly, a series of Er3+, Sm3+ co-doped Ba Gd F5 nanocrystalline phosphors have been synthesized by hydrothermal synthesis. Uniformly distributed nanocrystals with a spherical morphology and particle size of 30-40 nm were observed. Under the 382 nm radiation excitation, the Ba Gd F5 samples exhibit the typical green emission band of the Er3+ ions and the highly intense orange-red emission bands of the Sm3+ ions were attributed to the effective energy transfer from the Er3+ to Sm3+ ions, which has been justified through the luminescence spectra and the fluorescence decay dynamics.Chapter 4, up-conversion luminescence and synergistic effect of photons based on energy transfer of rare earth ions are explored. Up-conversion based on energy transfer of rare earth ions has extensive application prospects. Recently, a multitude of representative works of up-conversion have sprung up in solar cell-oriented application. The common ground of these works is the growing trend of broadband and efficient up-conversion. Herein, our research group proposed a new concept of photon synergistic effect, namely the high frequency and low frequency of light at the same time into appropriate intermediate frequency optical, which is a new way to realize the selective enhancement of emission. In this paper, we report the obtention of β-Na Lu F4 microcrystals doped with Er3+ ions by the surfactant-assisted hydrothermal. It was found that hexagonal prisms-like demonstrate intense up-converted luminescence(UCL) pumped by 1.54 mm infrared laser. More interestingly, a synergistic effect combined dual-mode(that is, down-conversion and up-conversion) with 7.9 % absolute enhancement rate of the red emission 659 nm(4F9/2 â†' 4I15/2) is witnessed in hexagonal prisms β-Na Lu F4:Er3+ phosphors by employing the dual wavelength 416 nm and 1.54 mm excitation source for the first time. By analyzing changes of photon number, we prove the existence of photonic synergistic effect.Chapter 5, our investigation is focused on the influence of reasonable doping on luminescence of rare earth ions with the crystal structure, doping and the energy transfer mechanism of phosphor. The phosphors Mg2Y8(Si O4)6O2:Tm3+, M3+, Eu3+(M =Tb, Dy) were synthesized by solid state reaction, and the photoluminescence properties under >350 nm excitation were studied. Under 357 nm excitation, the sample emitted white light, with the best color coordinate of(0.331, 0.337).Chapter 6, the paper summarizes the content of this study and the creative points, and forecasts the prospect of research directions.