Study On Optical Properties And Photoanode Application Of TiO₂/Rare Earth Doped Upconversion Materials

The contradiction between energy shortage and human demand forces researchers to focus on renewable energy.Therefore,solar cells that convert light energy into electricity have received widespread attention.Dye-sensitized solar cells（DSSCs）are considered as strong candidates for the third generation of solar cells due to their advantages of simple manufacturing process,low cost and high conversion efficiency.Among them,as a component of DSSCs,photoanodes play an extremely important role in capturing the energy of external light sources and converting it into electrical energy to work on external loads.Therefore,the photoanode should meet the following three points:first,it should load the dye and have the band gap width and energy level position matching with the dye;second,it should have good conductivity as a carrier migration platform;third,it can capture the most external light source energy.The hierarchical structure TiO₂has both large specific surface area and excellent photoelectric characteristics to meet the first two points,and the up-conversion material can meet the third point because of its own optical characteristics（anti Stokes shift）.Therefore,the composite materials combining the two perfectly meet the needs of the development of dye-sensitized solar cells.Facing the construction of high-performance photoanode materials,this paper carried out the research on the controllable preparation of hierarchical structure TiO₂,up-conversion NaYF₄:Yb³⁺Er³⁺nanomaterials,TiO₂/NaYF₄:Yb³⁺Er³⁺composite materials and photoanode films.The specific research contents are as follows:1.Firstly,the hierarchical structure of TiO₂was prepared by hydrothermal method.The morphology of the hierarchical structure of TiO₂was observed by scanning electron microscopy（SEM）and transmission electron microscopy（TEM）.The structure of TiO₂was analyzed by X-ray diffraction analyzer（XRD）.The optical properties of the hierarchical structure of TiO₂were studied by UV-Vis-NIR spectrophotometer and fluorescence spectrophotometer.2.Up-conversion NaYF₄:Yb³⁺Er³⁺nanomaterials were prepared by hydrothermal method.The morphology of up-conversion NaYF₄:Yb³⁺Er³⁺nanomaterials was observed by scanning electron microscopy（SEM）,and the optical properties of NaYF₄:Yb³⁺Er³⁺nanomaterials were studied by UV-Vis-NIR spectrophotometer and fluorescence spectrophotometer.The hydrothermal reaction time,reaction temperature,surfactant and other parameters were systematically investigated.The controllable preparation of monomer NaYF₄:Yb³⁺Er³⁺nanomaterials was realized,which laid the foundation for the subsequent composite of the two materials.3.A simple one-step hydrothermal method was developed to construct TiO₂@NaYF₄:Yb³⁺Er³⁺composite nanomaterials.The morphology information of TiO₂@NaYF₄:Yb³⁺Er³⁺composite nano-materials was studied by scanning electron microscope,and the optical absorption and emission characteristics of TiO₂@NaYF₄:Yb³⁺Er³⁺composite nano-materials were studied by UV-Visible-NIR spectrophotometer and fluorescence spectrophotometer.The controllable preparation of TiO₂@NaYF₄:Yb³⁺Er³⁺composite nanomaterials was realized.4.Using TiO₂@NaYF₄:Yb³⁺Er³⁺composite nano-materials as raw materials,the photoanode film was prepared by scraping method.The optical absorption and emission characteristics of the photoanode film of different materials were compared by using UV-Visible-NIR spectrophotometer and fluorescence spectrophotometer to improve the light capture ability of the photoanode film.