| The global economy has increased rapidly and the quality of people’s life has been significantly improved since the industrial revolution.However,the emission of greenhouse gases continues to increase on account of humans burn fossil fuels in large quantity,which has brought about climate change and serious environmental pollution.Therefore,the primary problem to be solved is to search for safe,clean and green new energy.In all of the renewable energy,solar energy has shown its advantages and potential in power generation.The wildly use of photovoltaic devices that directly convert solar radiation into electric energy is desirable from the perspective of energy conservation and environmental protection.The first generation of photovoltaic cells are silicon solar cells.As we all know,the conversion rate of silicon-based solar cells is very high,but it limited their wide application for the high cost of the modules and the complicated production process.Dye-sensitized solar cells have attracted the attention of researchers due to their low cost,easy preparation,no environmental pollution and high photoelectric conversion efficiency（PCE）.It is a sandwich structure composed of counter electrode,photoanode and electrolyte.The photoanode has dual function of light absorption and electron transport.It is of great significance to reduce the film thickness as far as possible but keep the light absorption.The main function of the counter electrode is to collect electrons from the external circuit to reduce the electrolyte.Most of the traditional dye-sensitized solar cells use metallic platinum as the counter electrode material,but the high cost of metallic platinum and the complex preparation process limit its wide application.Therefore,a large number of non-platinum counter electrodes have been studied.Among many materials,two-dimensional transition metal chalcogenides have attracted extensive attention due to their excellent electronic and photoelectric properties.In addition,studies have suggested that the heterojunction can regulate the transport direction of specific electrons and enhance the electrocatalytic reduction efficiency of the counter electrode.In this thesis,the structure of the TiO2 photoanode film was optimized by mixing a small amount of submicron TiO2into the nanocrystalline film to increase the light absorption.Transition metal chalcogenides heterojunction was prepared for the counter electrode with high efficiency.The research work of this thesis mainly includes the following aspects:（1）The photoanode film is usually a layer of nanocrystalline titanium dioxide（TiO2）deposited on the conductive glass because of their unique porous structure.The nanoparticle crystal film can absorb a large amount of dye but the particles are too small,it will hinder the electron transport and accelerate the recombination of electron hole pairs.In this thesis,the structure of the TiO2 photoanode film was optimized by mixing a small amount of submicron TiO2into the nanocrystalline film.The results shows that this hybrid photoanode can improve the light absorption thus enhance the photoelectric conversion efficiency.It provides a new and simple method for the preparation of efficient photoanode.（2）Pulsed laser deposition technology（PLD） and spinning coating method were used to deposit a layer of metal oxide films.Then they are converted to metal disulfide films in vapor phase.At last,four kinds of films,Mo S2/FTO,Re S2/FTO,Mo S2/Re S2/FTO and Re S2/Mo S2/FTO were obtained respectively.The results of cell assembly test show that the photoelectric conversion efficiency of Re S2/Mo S2/FTO is6.64%,which is higher than the efficiency of Pt（6.39%）,and deep higher than that of Mo S2/Re S2/FTO（5.26%）.In addition,WS2/FTO,Re S2/FTO,WS2/Re S2/FTO,Re S2/WS2/FTO and FTO/Re S2/WS2 have also been studied.The photocatalytic efficiency of Re S2/WS2/FTO is higher than that of WS2/Re S2/FTO.Through the above heterojunction preparation and testing,it is indicated adjusting the sequence of sulfide deposition could adjust the direction of electron transport.The valence band structure of type-II can enhance the separation and transfer of electron to improve sample photoelectric catalysis performance.The heterojunction structure is simple to prepare and corrosion resistant,which is conducive to the commercial application of dye-sensitized solar cells. |
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