The band alignment at the interface of an ITO/CuI heterojunction is studied by X-ray photoelectron spectroscopy (XPS). The measurements have been performed on samples obtained under the same experimental conditions as those used to achieve organic photovoltaic cells. The CuI upper layer was 3 nm thick. The semidirect XPS technique used to measure the band offsets allows us to estimate the band discontinuities at the interface ITO/CuI: ΔEv = 2.10 eV and ΔEc = 1.56 eV. This band alignment induces an increase of the work function of the anode when the structure ITO/CuI is used as electrode in organic solar cells for instance. As a matter of fact, the measurement, by means of a Kelvin probe, of the work function of the structures ITO/CuI, shows that it is significantly higher than that of ITO alone: 5.2 eV and 4.8 eV.
