Fabrication of Cu(In,Ga)S x Se 2-x films by one-step sputtering with elevated substrate temperature and their characterization

One-step sputtering with elevated substrate temperature was used to fabricate Cu(In,Ga)Se-2 (CIGSe) and Cu(In,Ga)S-2 (CIGS) films. We investigated the influence of this approach on the structure and electrical properties of CIGSe and CIGS films. Compact films with large grain size were achieved at relatively low substrate temperatures below 400 degrees C without post-treatments. The films obtained from CIGSe targets showed larger grain and higher crystallinity compared to that prepared from CIGS targets. It was found that the substrate temperature over 400 degrees C brought some undesirable effects on the film quality, such as voids and secondary phases. The loss of Ga and In during the fabrication process was detected, resulting in the formation of Cu-rich films with low carrier density. HBr solution etching reduced the Cu/(In + Ga) ratio of the sputtered films, leading to the improvement of the performance of the CIGSe solar cells along with the enhancement of carrier density.