Application Of Rare Earth Nanoluminescent Materials In Dye-sensitized Solar Cells

With the development of human society,the demand for energy has increased dramatically,and the search for clean and renewable energy is imminent.Solar energy is a renewable energy that meets global energy needs,and solar cells are the best way to convert light energy into electricity.Currently,dye-sensitized solar cells(DSSCs)have attracted great interest,and it is considered to be potential sources of renewable energy in third-generation solar cell technologies.However,there are still some shortcomings in DSSCs,such as poor long-term stability,narrow absorption spectra,charge carrier transport and collection losses,poor charge transfer mechanisms for dye molecule regeneration,etc.Therefore,how to use different methods to improve the performance of DSSCs and reduce the production cost has become one of the problems to be solved urgently.The use of rare earth luminescent materials as light converting agents to enhance light absorption is an effective means of increasing the efficiency of DSSCs.In this dissertation,several luminescent materials such as NaYF₄:Ln³⁺,Y₂O₃:Ln³⁺and CaWO₄:Ln³⁺have been introduced into the photoanode of DSSCs,and the efficiency of the cell has been significantly improved.The specific research results are as follows:(1)Preparation and application of NaYF₄:Er³⁺/Yb³⁺-C₃N₄ composite nanomaterials.NaYF₄ is a very effective luminescence host material,and g-C₃N₄ as a new type of metal-free semiconductor material has outstanding potential in energy conversion and storage.We have prepared NaYF₄:Er³⁺/Yb³⁺-C₃N₄ composite nanomaterials by hydrothermal and chemical adsorption methods,using the synergistic effect of NaYF₄:Er³⁺/Yb³⁺and C₃N₄ to improve the photoelectric conversion efficiency of dye-sensitized solar cells.(2)Preparation and application of Pt/Y₂O₃:Eu³⁺composite nanotubes.Y₂O₃ has excellent chemical and photochemical stability.After being compounded with noble metal Pt,Pt/Y₂O₃:Eu³⁺composite nanotubes were prepared.The effect of Pt content on the luminescent properties was studied.A Ti O₂-Pt/Y₂O₃:Eu³⁺composite photoanode was constructed.The experimental results show that the efficiency of the Ti O₂-Pt/Y₂O₃:Eu³⁺composite cell is 8.33%.Compared with the pure Ti O₂ cell,the photoelectric conversion efficiency of Ti O₂-Pt/Y₂O₃:Eu³⁺composite cell is improved by11.96%.The impedance results show that the interface resistance of Ti O₂-dye|I₃^-/I^-electrolyte interface of Ti O₂-Pt/Y₂O₃:Eu³⁺composite cell is much lower than that of pure Ti O₂cell.In addition,the Ti O₂-Pt/Y₂O₃:Eu³⁺composite battery shows longer recombination time and shorter transfer time than the pure Ti O₂cell.(3)Preparation and application of CaWO₄:Ln³⁺(Ln=Er and Tm)nanocrystals.Tungstate is a very important type of oxide material.We synthesized CaWO₄:Ln³⁺(Ln=Er and Tm)nanocrystals by solvothermal method,and studied the effect of Ln³⁺ion concentration on the morphology,size and luminescence properties of CaWO₄.For the first time,a Ti O₂-CaWO₄:Er³⁺composite photoanode was constructed.The results showed that the photoelectric conversion efficiency of the cell increased from 6.88%to8.33%after the incorporation of CaWO₄:Er³⁺.(4)We have also explored other matrix materials.The flower-like KY(Mo O₄)₂:Ln³⁺(Ln=Eu and Tb)microspheres with hierarchical structure were prepared by solvothermal method.The samples were characterized.The photoluminescence process of KY(Mo O₄)₂:Ln³⁺microspheres was systematically studied.