Solar cells made from wide gap chalcopyrites have received considerable interest due to the fact that high open circuit voltages are desirable for thin film modules and due to the goal to develop tandem solar cells. Although on theoretical grounds efficiencies of CuInS2 and CuGaSe2, solar cells should be comparable to Cu(In,Ga)Se-2 solar cells, so far, actual efficiencies are considerably lower. There are fundamental differences between the wide gap Cu-chalcopyrites and the low gap materials concerning the intrinsic dopability, the recombination defects and mechanisms, and the formation of the built-in potential.