Preparation Of Nanocrystaline Cu₃SnS₄ And Its Applications In Dye-sensitized Solar Cells

Crystal structures of Cu₃SnS₄(CTS)are mainly tetragonal,cubic and orthorhombic.As a P-type semiconductor,the electronic structure of CTS is similar to Cu S.Cu in the CTS has two valence states of+1 and+2,which leads to a high hole concentration(?10²² cm^-3)and metallic characteristics.CTS has a high light absorption coefficientof?10⁴ cm^-1and a wide bandgap range of 0.8 e V-1.7 e V.Nanocrystalline CTS has extremely high application value in the fields of gas sensors,dye-sensitized solar cells(DSSCs),and thermoelectric conversion due to the size effect.However,due to its structural diversity and wide bandgap range,it needs to be optimized and adjusted in practical applications.In this paper,we prepared nanocrystalline CTS and Cu₂Mn SnS₄(CMTS)powder and nanocrystalline films by methods fo solvothermal and spin coating,respectively.The namocrystaline films were used as counter electrodes for dye-sensitized solar cells.It is resuled that the the crystal structure and bandgap of nanocrystalline CTS were effectively adjusted by the addition of Mn.The mechanism of nanocrystalline CTS CEs in DSSCs were studied.The details are as follows:1.Crystal structure and morphology of nanocrystalline CTS and films were studied changing conditions of reaction time,manganese content and annealing treatment.It is found that prolonging the reaction time and annealing treatment are helpful for crystal growth,especially the nano-films prepared by spin coating with nanocrystalline CTS as the precursors.During annealing,the crystal structure transformed from nano-flakes into flower-like microspheres.2.Addition of manganese promoted the transformation of nanocrystalline CTS from orthorhombic phase to tetragonal phase.3.The photoelectric conversion efficiency?(%)of DSSCs based on the nanocrystalline CTS CEs is 6.32,and that of DSSCs based on the nanocrystalline CMTS/CTS CEs is 8.09.The addition of manganese can effectively improve the photoelectric conversion efficiency of the cell.