Preparation And Modification Of Double-layer CeO₂ Nanostructures And Its Application In Dye-sensitized Solar Cells

At present,the common problem faced by mankind is the energy problems,and these problems has been becoming more and more important due to the seriousness of environmental pollution and the depletion of fossil fuels.Solar energy as an inexhaustible and clean pollution-free ideal energy has become the most development potential of one of the new energy.Dye-sensitized solar cells have the advantages of low cost,simple process preparation,safe non-toxic and stable performance,and have good prospects for development.As one of the most important components of solar cells,light anode can be used to modify with different compositions and different structures,so as to improve the stability and conversion efficiency of dye-sensitized solar cells.The construction of light anodes need to consider the electronic transmission,dye adsorption and other factors.In this paper,double-shell CeO2 coating and doping methods were used to modify the photoanode and to explore the effect of different nanomaterials on the performance of dye-sensitized solar cells.Firstly,the CeO2 hollow spheres with double-shell structure were coated with TiO2 as the light scattering layer according to their special morphological structure,which reduce the electronic recombination,increase the electron transport rate.On the other hand,the double-shell CeO2 doped Er3+/Yb3+ upconversion material was prepared.Beacase of the electronic transition of rare earth ions to its luminous performance is limitedthe local surface plasmon resonance(LSPR)of the noble metal nanoparticles can be used to improve the upconversion fluorescence,thusleading to improve the performance of the battery and its photoelectric conversion efficiency.This paper focused on application of CeO2-based double-shell CeO2@TiO2 and upconversion CeO2:Er/Yb materials as photoanode materials for DSSC,this paper mainly includes the following three parts:(1)Firstly,double-shell CeO2 hollow spheres were synthesized via one-pot hydrothermal process,then the double-shell CeO2 hollow spheres were coated with a layer of TiO2 by sol-gel method,and double-shell CeO2@TiO2 hollow naospheres was prepared by calcination.The morphology,structure and phase of the materials were characterized by means of TEM,HRTEM,SEM,Mapping,XRD and EDS.The effects of hydrothermal temperature,hydrothermal time,the addition of sodium citrate and the amount of hydrogen peroxide on the morphology of double-shell CeO2 hollow spheres were investigated.The results show that the CeO2@TiO2 hollow spheres with double-shell structure have better diffuse scattering ability and the ability to adsorb dyes,so as to effectively scatter sunlight and improve the utilization rate of light.And it has reduced the electronic recombination,improved the electronic transmission rate,so that the photoelectric conversion efficiency of the battery has reached 7.95%,much higher than the P25,double-shell CeO2 hollow sphere samples.(2)Secondly,Au@SiO2 was prepared by sol-gel method,and then Au@SiO2@CeO2:Er/Yb composite was synthesized by hydrothermal method and calcination.HRTEM,SEM,XRD,TEM and UV-Vis were used to characterize the structure,composition and morphology,and the influence of the SiO2 shell thickness on the luminescence properties of CeO2:Er/Yb was investigated.The results show that the preparation of core-shell structure structure by noble metal nanoparticles will improve the photoluminescence intensity.Compared with the CeO2:Er/Yb composites the photoelectric transformation efficiency of the battery with Au@SiO2@CeO2:Er/Yb composite is improved.(3)Thirdly,double-shell structure CeO2:Er/Yb was prepared by hydrothermal method,SiO2 was coated by sol-gel method on the surface of double-shell structure CeO2:Er/Yb,after calcination,the Ag nanoparticles were loaded on the surface of SiO2 by in-situ reduction to synthesize CeO2:Er/Yb@SiO2@Ag composites.The structure,composition and morphology of the materials were characterized by means of SEM,XRD,TEM,HRTEM and UV-Vis.The effects of SiO2 shell thickness and the amount of silver nitrate on the up-conversion luminescence materials and the local surface plasmon resonance effect and luminescence properties of CeO2:Er/Yb were investigated.The results show that as a spacer SiO2 can protect the of double-shell CeO2 and provide an optimum distance for noble metal nanoparticles and up-conversion luminescent materials,which makes optimal photoluminescence intensity and the photoelectric conversion efficiency of the battery can be reached to 8.5%.