Fabrication And Research Of Silver And Germanium Co-doped Cu₂SnS₃ Thin Film Solar Cells

In this thesis,Cu2SnS3(CTS)thin films and their solar cells were prepared by solgel method,and the highest conversion efficiency of the CTS thin film solar cell with optimized components was 2.18%.Far less than the theoretical efficiency of more than 30%.The bottlenecks encountered by CTS solar cells are mainly the high series resistance and serious leakage caused by poor film quality,as well as the serious recombination due to high carrier concentration.Therefore,silver(Ag)and germanium(Ge)co-doping can effectively reduce the carrier concentration dominated by copper vacancy and also can improve the band gap of the CTS thin film after partially replacing Cu with Ag and Sn with Ge,respectively.As a result,we carried out a detailed experimental study on Ag and Ge co-doping.Firstly,the effects of only Ag doping on the properties of CTS thin film and solar cells were investigated.The successful incorporation of silver into CTS thin film was confirmed by a series of characterization methods such as EDS,XRD and Raman,and the Ag-doped content was also verified.The morphology,optical and electrical properties of CTS films with different Ag-doped contents were characterized by SEM,UV spectrophotometer and Hall test system.The results demonstrated that the Agdoping not only was beneficial to the growth of grains but also increased the band gap and reduced the carrier concentration to some extent.The J-V curves of CTS thin film solar cells doped with Ag contents of 0、3%、6%、9%were tested.It was found that the optimal cell efficiency was 2.78%when the Ag-doped content was 6%,and the open circuit voltage was greatly improved.Then,on the basis of 6%Ag doping,different Ge doping was carried out to prepare Ag and Ge co-doped CTS films and their solar cells.The doping of germanium into CTS thin films was verified by basic phase detection,and the SEM test showed that the Ge-doping optimized the grain boundaries of the CTS thin film.Then the basic parameters of Ag and Ge co-doped CTS thin film solar cells were performed.It was found that the doping of Ge was conducive to solve the problem of low short-circuit current density of solar cells caused by the doping of Ag alone.After the external quantum efficiency spectra were tested,it was found that the Ge doping indeed improved the larger band gap value in the double band gap of monoclinic CTS thin film,but the smaller band gap value did not increase significantly.For CTS thin film solar cells with different Ge-doped contents of of 0,3%,6%and 9%,the performance of thin-film solar cells showed the best when the content of Ge doping was still 6%.In conclution,in this study,the highest efficiency of pure CTS thin film solar cell was 2.18%,which increased to 2.78%after optimized Ag doping,and the final efficiency was 3.15%after optimized Ag and Ge co-doping,which demonstrated that Ag and Ge co-doping was an effective way to improve the efficiency of CTS thin film solar cells.