Chalcopyrite semiconductors for highly efficient thin-film solar cells

In this contribution the material properties of polycrystalline (Cu,Ag)(In,Ga)(S,Se)2 thin films and their suitability for heterojunction solar cells are discussed. The copperchalcogenides play an important role in the formation of these films. However, a deteriorating impact of these secondary phases on the cell performance exists. Methods to overcome this dilemma are presented. The role of the morphology and of the chemistry of grain boundaries is illustrated in the CuGaSe2 and CuIn(S,Se)2 system. Important parameters for the design of a heterojunction solar cell are discussed. During the course of this work solar cells with efficiencies exceeding 14% could be obtained.