Valence band alignment at the CuI/CuInS/sub 2/ heterointerface

We studied the valence band alignment at the interface between polycrystalline CuInS/sub 2/ thin films and p-type transparent semiconductor CuI. We used X-ray photoelectron spectroscopy to determine the binding energy of the valence band maximums (VBM) at the interface between the polycrystalline film of CuInS/sub 2/ and evaporated CuI layer. Assuming a constant spacing between VBM and the core energy levels and using parabolic approximation with broadening for the density of states near the VBM, we conclude from the experimental results that the band alignment at the interface between the CuInS/sub 2/ polycrystalline films and the CuI films involves a discontinuity preferentially of a spike type, being smaller than 0.2 eV. A band alignment with no band offset or with a small spike is optimal for solar cell applications.