Synthesis Of ZnO Composite Nanomaterials And Their Application In Dye-sensitized Solar Cells

With the rapid development of technology and society,traditional energy resources are gradually exhausted,and the environmental pollution is increasing.Finding safe,clean,and green new energy is needed to be solved by mankind.The most promising new energy is definitely solar energy.In a series of solar cells,dye-sensitized solar cells(DSSCs)have attracted the attention of researchers due to their low manufacturing cost and high photoelectric conversion efficiency(PCE).Among them,the counter electrode and photoanode materials are important to the photoelectric conversion efficiency of DSSCs.The most commonly used photoanode material in DSSCs is titanium dioxide nanoparticles,but the porous film formed by the accumulation or agglomeration of nanoparticles has a slow electron mobility to hinder the conduction of electrons.Therefore,using one-dimensional nanomaterials can increase the electron transmission length,reduce the charge recombination in the anode,and thus improve the photoelectric conversion efficiency.The main role of the counter electrode is collecting the electron froms the external circuit and catalyzing the reduction reaction in the electrolyte.Usually metallic platinum was used as the counter electrode material.However,the large-scale application of Pt is limited due to its high cost.So finding a new non-Pt counter electrode materials has become a new research topic.Among many materials,transition metal chalcogenide compounds play an important role in the field of optoelectronics,especially in the field of batteries,due to their good electrical conductivity,excellent catalytic activity and high electron mobility.In this thesis,the ZnO/TiO₂ multipod nanostructures grown with TiO₂nanoparticles as cores are used as the photoanode of dye-sensitized solar cells,and the two-dimensional transition metal chalcogenide compounds are used as counter electrodes.(1)ZnO multipod nanostructures are widely used for their unique structures.However,the large-scale synthesis of these materials is a challenge for the practical applications.In this paper,we used a hetero-seed mediated hydrothermal method to synthesize ZnO/TiO₂ multipod nanostructures with ultra-high yield.The TiO₂nanoparticles were used as the seeds and nucleated centers for the following ZnO nanorods growth,in which these ZnO nanorods scattered from the TiO₂nanoparticles to form ZnO/TiO₂ multipod nanostructures.The diameter and length of these ZnO nanorod branches were controlled by the amount of TiO₂nanoparticles.The yield of pure ZnO/TiO₂ multipod nanostructures can reach 20.0g/L within 20 min heating time.When used as the anodes of dye-sensitized solar cells(DSSCs),a photoelectric conversion efficiency of 3.1%has been achieved when using these ZnO/TiO₂multipod nanostructures as the anodes of DSSC.This is due to the one-dimensional(1D)nanostructures are promising by fastening electron transport to reduce the charge recombination.As a result,this provides a simple method to synthesize ZnO/TiO₂multipod nanocomposites with high yield and low cost,which can be used as the anodes for high efficient DSSCs and photocatalysts.(2)Using pulsed laser deposition(PLD),a layer of Mo O₃(Co₃O₄)film was deposited on FTO conductive substrate.Then a layer of Co₃O₄(Mo O₃)film was deposited on the pre-deposited thin film to finally get four kinds of films FTO/Mo O₃,FTO/Co₃O₄,FTO/Mo O₃/Co₃O₄,FTO/Co₃O₄/Mo O₃.Then using chemical vapor sulfurization method to sulfurze these four film samples to FTO/Mo S₂,FTO/Co S₂,FTO/Mo S₂/Co S₂,FTO/Co S₂/Mo S₂ film.When used as the counter electrode of DSSCs,I-V curves show that the photoelectric conversion efficiency of FTO/Co S₂/Mo S₂ is 6.42%,which is similar to the efficiency of Pt(6.58%),higher than FTO/Mo S₂/Co S₂(5.02%).So its photoelectric conversion efficiency as the counter electrode of DSSCs can be comparable to Pt.But the cost is lower and the reserves are more abundant,which is ideal to the commercial application of dye-sensitized solar cells.