Enhanced the crystallinity of Cu(In, Ga)Se2via an improved silver-treated process

As we know, the quality of the CIGS film is important for the improvement of device performance: an improved crystallization can reduce the bulk recombination of the absorber layer. In this work, different silver (Ag) treatment processes are employed to improve the CIGS film quality after three-stage deposition process. We find that the grain size and crystallinity of CIGS films are considerably enhanced by increasing the deposition temperature and annealing time. The growth mechanisms of Ag treatment process could be visually displayed by the new reaction models of Ag treatment process. According to the XRD results, we have demonstrated that the element Ag contributes to the (112) preferred orientation of the absorber layer, which has the lower surface energy compared with (220)/(204) preferred orientation of CIGS film. With appropriate Ag-treated process, both electrical and optical properties of device are enhanced. And the best Ag-treated CIGS solar cell with the conversion efficiency of about 17.1% has a relative increase of about 11.8% in contrast with that of the reference CIGS solar cell.