Preparation Technology Of Sb₂S₃ And CoS Thin Films And Their Applications In Dye-sensitized Solar Cells

As a kind of direct band gap semiconductor materials,metal chalcogenides have been extensively applied in dye-sensitized solar cells due to their unique photoelectric properties and excellent photosensitivity.It is the focus of the present research to explore the suitable preparation technology of metal sulfide thin films and improve the photovoltaic efficiency of dye-sensitized solar cells.Based on the above background,three aspects of research work in this thesis were carried out as follows:First,a quick sequential deposition method was developed for the fabrication of metal sulfide thin films,namely,in situ solid-gas reaction method.The method includes deposition of a metal precursor through spin-coating process,and subsequentally converting into the corespongding metal sulfide thin films through reaction with hydrogen sulfide gas.Compared with the traditional preparation method of metal sulfide thin films,this method is easy and quick for the depositon of the metal sulfide thin films,and the amount of the sulfides can be easily controlled throuth adjusting the precursor concentration and spin-coating parameters.More importatlly,the impurity of the oxdides were well avoided in the film prepared by this method.Second,Sb₂S₃-sensitized TiO₂ photoanode was prepared using the in situ solid-gas reaction method.SbCl₃ was first dissolved in ethanol and formulated into precursor solutions with concentrations of 10 wt%,13 wt%,16 wt%,19 wt%,22 wt%and 25 wt%,respectively.Then,Sb₂S₃ thin film was deposited onto mesoporous TiO₂films by in situ gas-solid reaction method.The effects of precursor solution concentrations and hole transporting material concentrations on the structure,morphology and photovoltaic performance of Sb₂S₃ thin films were investigated.The results indicated that the optimum concentration of the precursor solution is 16 wt%and the optimum concentration of the hole transport material is 15 mg/mL.The device performance was further optimized by cooling Sb₂S₃ immediately and adding the hole extraction layer PEDOT:PSS,with a maximum conversion efficiency of 6.27%.Third,CoS counter electrode was prepared by in situ solid-gas reaction method,and applied into dye-sensitized solar cells.The surface morphology,material structure,electrocatalytic and photovoltaic performances were characterized by SEM,XRD,raman spectroscopy,XPS,EIS,CV,Tafel polarization curves and J-V.The result showed that CoS prepared by 20%concentration had highest electrocatalytic activity as a counter electrode（CE）.Under standard illumination of one sun(100 mW·cm^-2),the dye-sensitized solar cell（DSSCS）incorporating CoS-decorated FTO glass substrate as a CE provide a power conversion efficiency（PCE）of 7.81%,which are comparable with the values obtained for the device with a Pt-based counter electrode（PCE:7.97%）.The results indicate that CoS film prepared by 20%concentration deposited by the solid-gas reaction approach exhibits high catalyst ability and low cost,which can replace Pt as a counter electrode for dye-sensitized solar cells.