Research On Multi-interface Synergistic Effect And Mechanism In DSSCs Counter Electrode Materials

With the increasing population in the world,the demand for energy is also increasing.The current energy mainly comes from fossil fuels,such as oil,coal,natural gas and so on.However,with the continuous consumption of fossil fuels,the environmental problems caused by the lack of energy and the use of fossil fuels have become increasingly prominent.Therefore,human beings are actively exploring clean and pollution-free energy,because clean energy can effectively alleviate the current energy shortage and environmental pollution,which is of great significance to the sustainable development of society in the future.Among them,solar energy is regarded as one of the cleanest energy sources,and its reserves are the largest energy sources that can be developed in the world.In this sense,the energy of the sun is inexhaustible.The large-scale utilization of solar energy is used to generate electricity.There are many ways to use solar energy to generate electricity.There are two kinds of practical ones:(1)Light-heat-electricity conversion,that is,using the heat energy generated by solar radiation to generate electricity;(2)Light-electricity direct conversion,its basic principle is to directly convert solar radiation energy into electric energy by using photovoltaic effect,and its basic device is solar cell.Among them,the energy conversion by solar cells is very convenient and efficient,and researchers pay great attention to it.At present,solar cells have developed to the third generation,mainly including perovskite solar cells,organic solar cells and dye-sensitized solar cells.Among them,dye-sensitized solar cells have become one of the current research hotspots because of their simple structure and high photoelectric conversion efficiency.However,the precious metal platinum is usually used as the electrode material,which leads to the high cost of the cell and hinders its large-scale application.At present,the earth's abundant excess metals are considered as an effective and ideal substitute for precious metal electrodes.However,due to fewer active sites and weak intrinsic activity,the overall performance is not ideal.Therefore,it is necessary to deeply understand the reaction process and the source of catalytic activity of the electrode materials in the whole cell.On this basis,the electrode materials with low cost and high efficiency can be designed and constructed reasonably.Aiming at the core scientific problem of the influence of counter electrode materials on photoelectric conversion efficiency in dye-sensitized solar cells,this paper focuses on the synthesis and design of focusing materials to improve the performance of the cells.The morphology of the synthesized material was observed by scanning the electron microscope and transmission electron microscope.At the same time,the relationship between the local structure and catalytic activity of electrocatalytic materials was studied by X-ray diffraction,Raman spectroscopy,photoelectron spectroscopy and high-resolution X-ray absorption spectroscopy.It provides experimental and technical basis for the synthesis of efficient electrode materials.The main research contents of this paper are as follows:1.Study on the design and performance of pure carbon materials as counter electrode materials:The pure carbon materials with different morphologies are prepared as the electrode in dye-sensitized solar cells,controlling the specific surface area of carbon materials to increase the active sites;The mesoporous materials are used to accelerate the electron transmission speed,thus accelerating the redox reaction rate.Electrochemical tests show that large specific surface area and porous structure can significantly improve reaction kinetics and enhance photoelectric conversion efficiency.2.Study on the performance of Fe3O4/Ni@NC nanocomposites as electrode materials:Fe₃O₄/Ni@NC nanocomposites were synthesized by pyrolysis in one step,which has an effective interface and effectively combines the excellent properties of Fe₃O₄ and Ni.In addition,nitrogen-doped carbon effectively encapsulates it,and further accelerates the reaction kinetics through an efficient electron transfer path.At the same time,the introduction of nitrogen can effectively introduce defects and enhance the catalytic activity of the material.3.Constructing multi-interface structure to improve the catalytic activity and cycle stability of solar cells:A multi-step transformation method,firstly fixing NiS nanosheets on the surface of N-doped hollow thin-shell carbon spheres(NHCS),and then encapsulating with reduced graphene oxide(RGO)to form NHCS/NiS/RGO nanocomposites.The interface charge distribution behavior of the counter electrode in DSSCs was investigated.It is found that interface charge polarization with larger RGO surface area promotes charge transfer,and NiS nanosheets evenly distributed on NHCS surface gather electrons,which leads to strong interface coupling,and further promotes charge transfer and oxidation and reduction of triiodide,which has obvious multi-interface electrode activity.4.The effective strategy of interface engineering and structural integration and its performance in solar cells:(N-CHS/(Ni₃B/NiO)/RGO)nanocomposites are formed based on the integration of N-doped carbon hollow spheres(N-CHS),graphene(RGO)and Ni₃B/NiO heterojunction.X-ray absorption spectroscopy(XAS)is used to solve the local interface structure of a given material.The introduction of RGO not only enhances the strong coupling between Ni and B,but also promotes the formation of Ni₃B/NiO heterostructure.In addition,the introduction of RGO can also promote charge transfer and accelerate reaction kinetics.In electrochemical tests,the interface structures with different NiO contents show different reaction dynamic processes.Finally,revealing the reaction kinetics mechanism of dye-sensitized solar cells from the structural integration and interface engineering of N-CHS/(Ni₃B/NiO)/RGO electrode materials provide a powerful strategy.