Oxidative etching treatments based on bromine water mixtures have been studied on polycrystalline thin films of Cu(In,Ga)Se2. This treatment enables preparation of planar, smooth and specular surfaces whose chemical properties are well defined, despite the small thickness of the layers (≈2 µm). After device completion, the electronic properties (I–V curve, spectral response) were studied and correlated to device performances. Theses conditions allow to re-engineer damaged or aged surfaces of CIGS and to recover high photovoltaic performances. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)