We investigated CuInSe2 (CIS) based solar cells with InxSey (IS) deposited by evaporation and CdS deposited by the Chemical Bath Deposition (CBD) method, as buffer layer. I–V measurements gave the following output parameters for cells fabricated using IS as buffer: Jsc= 30.8 mA/cm2, Voc = 0.44V, FF ≈ 0.6 and η = 8.3 % with 100 mW/cm2 irradiance. Solar cells fabricated using a CdS buffer layer deposited on a CIS substrate prepared under the same conditions as those employed in the fabrication of CIS/ IS/ZnO cells, gave the following results: Voc = 0.43 V, Jsc = 34 mA/cm2, FF ≈ 0.63 and η = 9.2%. Auger Electron Spectroscopy (AES) depth profiles measurements were carried out to identify possible diffusion processes affecting the cell operation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)