Preparation Of Transition Metal Sulfide Counter Electrode And Its Application In Dye-sensitized Solar Cells

Solar energy is one of the most likely new energy sources for large-scale application due to its inherent advantages of wide distribution,convenient access,huge reserves,low cost of photovoltaic technology,safety and pollution-free and other inherent advantages.Solar cell technology has built a system including silicon-based solar cells,compound thin film solar cells,dye-sensitized solar cells,perovskite solar cells with decades of technological innovation and development.As the third generation solar cell,dye-sensitized solar cell(DSSC)show a bright future because it is irreplaceable advantages of low cost,green environmental protection,short energy recovery cycle,flexible design,outstanding outdoor performance and high conversion efficiency of double-sided battery.Counter electrode(CE)is an important component of DSSC devices.As a common catalyst,Platinum CE tends to increase the cost,lost its activity because of the by-products generated in iodide electrolyte,and destroys the stability of the DSSC.Multiple transition metal compounds not only have good conductivity and catalysis,but also have the advantages of low price and stable performance.In this paper,MoIn2S4 and MoInSnS,two kinds of multicomponent CE materials are introduced.Their catalytic and photoelectric properties in DSSC devices are studied.The specific research work is as follows:(1)New ternary transition metal compounds MoIn2S4 based on FTO have been successfully prepared by one step hydrothermal method.The surface morphology,element composition and crystal structure of MoIn2S4 were characterized by SEM,XRD,XPS and BET.The results show that the MoIn2S4 with petal like nanoflake array structure synthesized by middle content of InCl3 has the largest specific surface area,which will fully expose more catalytic activity sites and accelerate the reduction of I3-in the electrolyte.Several electrochemical tests,including cyclic voltammetry(CV),electrochemical impedance(EIS)and Tafel curve,have confirmed that MoIn2S4 CE synthesized with middle content of InCl3 has the minimum charge transfer resistance Rct,the maximum exchange current density J0 and the limit diffusion current density Jlim between the interface of electrolyte and CE,so it has the highest conductivity and electrocatalytic activity.The photoelectric conversion efficiency of the assembled cell is 6.51% under the illumination of 100 m W cm-2,which is slightly better than that of the Pt based.(2)CNTs doped composite CE can exert the synergistic effect and enhance the photoelectric properties of materials.Different CNTs content was added in the precursor solutions which were optimized aboved,and the MoIn2S4@CNTs composite CEs were prepared by hydrothermal method.It is confirmed that the MoIn2S4@CNTs-2 CE with 0.02 g CNTs doped has the structure of hedgehog spherical nanosheet array structure and the largest specific surface area tested by BET.MoIn2S4@CNTs-2 CE has the smallest Rs and Rct,and the largest J0 and Jlim by electrochemical tested.The photoelectric conversion efficiency of DSSC assembled with the CE is as high as 8.38%.Compared with the non CNTs doped Mo In2S4 CE,the photoelectric performance of the MoIn2S4@CNTs CEs is significantly improved,which is due to the unique structure and good physical and chemical properties of CNTs.(3)On the basis of the preparation of the ternary compound MoIn2S4,a quaternary MoInSnS compound thin film with a surface morphology of petal-like nano-array spherical particles was synthesized by adding a new element Sn.It was confirmed that the spherical particles of this MoInSnS nanosheet array showed better catalytic activity when reducing I3-ions after tested by CV,EIS,and Tafel curves.The DSSC assembled with a porous TiO2 photoanode has achieved a PCE of 7.17% under standard solar light intensity.