In a standard chalcopyrite-based thin film solar cell, the formation of the heterojunction is mediated by a thin buffer layer. This buffer is prepared by chemical bath deposition of CdS. The cell is completed by an undoped ZnO film followed by the highly doped transparent front contact. An alternative structure without any buffer layer where the undoped ZnO is replaced by (Zn,Mg)O has been suggested previously by Minemoto et at. [T. Minemoto, Y. Hashimoto, T. Satoh, T. Negami, H. Takakura, Y. Hamakawa, J. Appl. Phys. 89 (2001) 8327]. By adapting and applying this approach to CuInS2 absorbers from industrial pilot production we achieved efficiencies of 8% for small area cells (as compared to 9.4% for a reference cell with CdS buffer) as well as monolithically integrated test structures. (C) 2009 Elsevier B.V. All rights reserved.