Photovoltaic devices based on Cu(In,Ga)Se-2 with Cd-free buffer layer exhibit worse photovoltaic parameters and more pronounced transient behavior than standard CdS-buffered structures. In this work the electrical characteristics of the cells with ZnO buffer obtained by atomic layer deposition technique are compared to those of baseline CdS/CIGS cells. Persistent changes induced by light soaking and reverse-bias soaking in the current voltage characteristics, admittance and DLTS spectra are analyzed. We discuss a role of buffer layer for the enhanced net doping in the interfacial region of absorber, Fermi-level pinning and conduction band offsets at the heterointerface for the photovoltaic performance of the cell. (C) 2004 Elsevier B.V. All rights reserved.