For production-related research and development of CIGS thin-film solar cells it is essential to deposit the light-absorbing CIGS material in the shortest possible time. In the SpeedCIGS project funded by the German Federal Ministry of Economic Affairs and Energy BMWi, ZSW identifies, in coopration with sechs partners, the maximum growth rates possible. Process optimizations are achieved mainly by detailed investigations into the course of growth within the ZSW‘s inline co-evaporation plant. Scanning electron microscopic images of the grain structure, as well as a depth profile of the composition by means of GD-OES (glow discharge optical emission spectroscopy) yield valuable insights into the process control, e.g. the influence of alkaline metals on the course of growth and the energy conversion efficiency.