Effect of rapid thermal annealing on the compositional ratio and interface of Cu(In,Ga)Se2 solar cells by XPS

► RTA treatment makes the compositional ratio of Al and Zn increase. ► RTA treatment improves the content of Se in CIGS thin film. ► The ratio and shape character of Cu/(In + Ga) and Ga/(In + Ga) are further optimized. ► Compared with un-annealed sample, the absolute efficiency improvement is about 1.2%.