Photon Synergistic Effect And Modification Of Structure And Phase For Energy Conversion Materials

Energy-converted materials are used widely in optics, magnetics, and electricity fields. The studyof photoluminescence energy-converted materials involves several key fields, such as laser materials,solar cells, biological fluorescence label, display materials, and long afterglow phosphor and so on.The energy transfer mechanism in the photoluminescence process, and the influence of crystal fieldon luminescent centers, are the main factors to suppress high fluorescence quantum yield. To enhanceluminescent efficiency, we proposed a physical model of the synergistic effect of the ultraviolet andinfrared photons, and designed relevant experiments to explore the possibility of the proposedphysical model. To explore the influence of redistribution of internal charges on the synthesismechanism and optical properties, we studied the phase structure and fluorescence modifications ofmetal ions doped energy-converted materials. The thesis is organized as follows:1. The species, application feature, and preparation methods of the Rare-earth ions dopedenergy-converted materials were introduced. We introduced the development status of solar cells, andpropose some methods to increase photovoltaic effect through optical means.2. We proposed the synergistic effect of ultraviolet and infrared photons. We synthesized Er3+dopedYbF3and NaGdF4phosphors to check the possibility of synergistic effect. The change trend of thetransient and steady-state spectra was studied by employing single-mode and dual-mode excitationsources. The synergistic effect of ultraviolet and infrared photons was realized in the Er3+doped YbF3phosphors under369nm and980nm dual-mode excitation. The maximal absolute enhancement rateof658nm red emission was10.43%. The synergistic effect of ultraviolet and infrared photons wasrealized in the Er3+doped NaGdF4phosphors under370nm (or442nm) and1.54μm dual-modeexcitation. The maximal absolute enhancement rate of658nm red emission was42.2%. Thepossibility of synergistic effect was proved through analyzing the number of infrared photons andlifetimes of the red emission. The photon synergistic effect is a novel method to reduce thesub-bandgap and thermalization losses caused by ultraviolet and infrared photons in photovoltaicconversion.3. We offered an idea to obtain white light LED with blue excition source. We synthesizedEu3+/Ho3+doped TGNL glass, and analyzed the transient and steady-state spectra of the glass. Theemission spectra of the glass can be converted to the Commission International de I’Eclairage (CIE)1931chromaticity diagram. The luminescent color changes from green, through yellow, and finally to red. As a result, some color-tunable luminescence emissions were obtained. We thought thatcolor-tunable luminescence emissions were modified by an energy transfer from Eu3+to Ho3+ions.This work offeres a new method to resolve the poor color rendering index of YAG:Ce3+phosphors.4. We realized to control optical properties by controlling shapes of some phosphors, and exploredthe influence of specific morphological shapes of nanodisks, nanorods and microtubes on thephotoluminescence and inner photoelectric effect of single Na1.23Ca0.12Y1.28Er0.24F6phosphor. Wesynthesized hydrothermally hexagonal Na1.23Ca0.12Y1.28Er0.24F6nanodisks, microtubes, and nanorods,and obtained luminescence emissions by exciting nanodisks, microtubes, and nanorods with a980nmlaser. As a result, the nanodisks, microtubes, and nanorods emited blue, orange, and red luminescence,respectively. Additionaly, the Na1.23Ca0.12Y1.28Er0.24F6nanodisks, microtubes, and nanorods alsoshowed inner photoelectric effect behaviors under980nm excitation. Simultaneous control ofhomochromatic luminescence and inner photoelectric effect were achieved by modifyingmorphological shapes of single Na1.23Ca0.12Y1.28Er0.24F6phosphor.5. We explored the modification of redistribution of internal charges on the shape, phase, structure,and optical properties. We synthesized hydrothermally Bi3+, Al3+, Gd3+, or Yb3+doped BaF2and SrF2,Pr3+doped NaYF4:18%Yb3+/2%Er3+, and Ca2+or Er3+doped NaGdF4. The change trend of shape,phase, structure, and optical properties of above phosphors was obtained by analyzing the images ofSEM, TEM, EDS, and spectra. The electron density difference of metal ions doped BaF2and SrF2wascalculated according to the density functional theory. We proposed a modulation principle of shape,phase, and structure of the BaF2and SrF2crystals induced by the redistribution of internal charges.6. We offered an idea to realize simultaneously anti-reflection and light-conversion in single thinfilm. We synthesized Y2O3: Er3+porous pyramid arrays by different templates of the polystyrenecollidal microsphere, in which the micropore sizes can be controlled. The transmittance spectra ofY2O3:5%Er3+porous pyramid arrays showed that the transmission ratio could be controlled byadjusting micropore diameter sizes. The fluorescence spectra of porous pyramid arrays showed that1.538μm infrared light was upconverted to green, red and infrared luminescence. The intensity of redemission band of Y+2O3:5%Er3,5%Li+pyramid arrays was about19times greater than that of thesample without Li+. The intensity of infrared emission band is about3times greater than that of thesample without Li+. The Y2O3:5%Er3+porous pyramid arrays with the roles of anti-reflection andlight-conversion could be used as optical coating of the solar cells.At last, we gave a summary of the thesis and prospect of future works of multi-photons synergisticeffect and bifunctional nanoparticle with the anti-reflection and light-conversion functions.