Study On The Solvothermal Synthesis Of Cu₂SnS₃Type Of Compounds And Their Properties

Solar energy is clean and abundant and it has been considered to be one of the mostpotential renewable energies. Photovoltaic technology is an important way to theutilization of solar energy. Thin film solar cells have gained widely attention because ofthe potential for a significant reduction in the electricity generation. Cu₂SnS₃andCu₂ZnSnS₄semiconductor compounds that have direct band gap, with band gap widthsuitable for the absorption of the solar spectrum, and thus they have great prospects forphotovoltaic application. In this study, we focus on the preparation of Cu₂SnS₃compound and the reaction of Cu₂SnS₃to Cu₂ZnSnS₄.We synthesized Cu₂SnS₃nano-particles by solvothermal method, usingCuCl₂2H₂O, SnSO₄, S as reactants, ethylenediamine as solvent,200℃for24h. Thenanoparticles were used to prepare ink, and Cu₂SnS₃thin films were fabricated throughspin-coating the ink on a glass substrate and annealing. The solvothermally synthesizedCu₂Sn(S_1-xSe_x)₃compounds have smaller particles size, reduced lattice content, andsmaller band gap width with increasing Se content. We use GeCl4as Ge source andsynthesized Cu₂(Sn_1-xGe_x)S₃with different Ge content by solvothermal method. XRDand UV-vis test results show that Cu₂(Sn_1-xGe_x)S₃compounds’ lattice constants andband gaps change linearly with Ge elements proportion. This result indicates that Snelement in Cu₂SnS₃can be replaced by Ge elements, and it is possible to control theSn/Ge ratio to adjust and optimize the band gap width of Cu₂SnS₃compound, and thusto improve power conversion efficiency of the solar cells. With the reaction of preparedCu₂SnS₃particles and ZnS particles, we obtained Cu₂ZnSnS₄compound particles. Wealso synthesized Ge doped Cu₂ZnSnS₄compound by the reaction of ZnS and Ge dopedCu₂SnS₃compound.In summary, we studied the solvothermal synthesis of semiconductor compoundsof Cu₂SnS₃type. The substitution of S by Se and substitution of Sn by Ge in Cu₂SnS₃can adjust the band gap of the compounds. These results are of significance on the studyof other chalcogenide semiconductor compounds. using the two-step method tosynthesize Cu₂ZnSnS₄compound, we provide an important methodology for the synthesis, elements substitution, and the reaction path studies of Cu₂ZnSnS₄compounds.