Study On Fabrication Of CuSbS₂ Thin-film Solar Cells By Sulfurization Of Pulse Electrodeposited Sb/Cu Metal Precursors

Copper antimony sulfide（CuSbS₂）is a new type of direct band gap semiconductor material,its band gap can be adjusted in the range of 1.4～1.6 e V,high light absorption coefficient(>10⁵cm^-1),low crystal grain growth temperature（300～400℃）.Therefore,it is considered to be one of the promising candidates for manufacturing flexible thin-film solar cells.Electrodeposition is highly praised by researchers due to its advantages of high material utilization,fast deposition rate,and low cost.In this paper,CuSbS₂thin film solar cells were fabricated by pulse electrodeposition two-step post sulfurization method,and the research was carried out around the problems of large roughness of Cu-Sb metal preform layer,excessive loss of Sb element during sulfurization,and more impurity phases.The specific research results are as follows:The smooth,compact and highly crystalline CuSbS₂film can significantly improve the performance of devices.However,the direct electrodeposition of Cu on Mo substrate tends to produce"dendritic"clusters,resulting in larger surface roughness of Cu layer.It is easy to obtain rough Cu/Sb metal precursors by redeposition of Sb layer on such rough Cu layer,which makes it difficult to obtain CuSbS₂film with uniform composition distribution in subsequent sulfurization process.In this paper,a Sb buffer layer was deposited on Mo substrate,and then a Cu layer was deposited on a smooth Sb layer to obtain a Sb/Cu precursors with smooth surface and uniform grain size.In this paper,the effects of different sulfurization processes and the ratio of Sb/Cu atoms on the morphology,composition and phase of thin films have been systematically studied.The results showed that the CuSbS₂film prepared by one-step sulfurization process had many impurity phases,and the film crystallinity was poor;The optimized two-step sulfurization process can be used to prepare phase pure CuSbS₂films with better crystallinity.After optimizing the two-step sulfurization process and adjusting the Sb/Cu atomic ratio of the metal precursors,the content of Sb element in the film was increased and the impurity phase of Sb₂S₃was significantly reduced,and the crystallization degree of CuSbS₂film were significantly improved.The growth mechanism of CuSbS₂film was studied.It was found that Cu S did not react with Sb₂S₃completely in the film at 300-340℃,and the impurity ratio of Sb₂S₃in the film was large,resulting in poor crystallinity of the film.With the increase of annealing temperature,the reaction between Cu S and Sb₂S₃was strengthened.CuSbS₂films with good crystallization degree were obtained at 360℃.However,CuSbS₂phase changed into Cu₃Sb S₄phase when the temperature rose to400℃.Through process optimization,CuSbS₂thin film solar cells with the highest photoelectric conversion efficiency of 0.90%were obtained.