This paper explores the influence of hydrogen peroxide H2O2 on the chemical bath deposition of zinc oxisulfide Zn(S,O) and the final photovoltaic performances of the Cu(In,Ga) Se-2-based (CIGSe) associated device. First, the influence of H2O2 on Zn(S, O) deposition rate and growth mechanism is studied with theoretical considerations and in situ quartz crystal microgravimetry measurements. It shows that hydrogen peroxide concentration masters the deposition rate and induces a "cluster-by-cluster" mechanism. Morphology and composition of Zn(S, O) films have been investigated by scanning electronmicroscopy and X-Ray photoelectron spectroscopy techniques. In a second part the optimized process is then on co-evaporated Cu(In,Ga) Se-2 substrates and solar cells are completed with a (Zn,Mg) O/ZnO:Al window layers. The use of H2O2 leads to lower efficiency than CdS-based reference, which can be explained by an oxidation of the CIGSe surface. (C) 2016 Elsevier B.V. All rights reserved.