Interphase characterization at the n–CuInSe2/I−–I2 acidic electrolyte contact

The chemical nature of a photoelectrochemically formed film at the n–CuInSe2/I−–I2–HI–Cu+ electrolyte interface is determined. Grazing incidence x-ray diffraction reveals a phase consisting of polycrystalline CuISe3 with elemental Se patches. Ultraviolet photoelectron spectroscopy (UPS) identifies the interphase as a p-type semiconductor. Evidence for the film character of p–CuISe3–Se0 is presented. Flat-band potential, net acceptor density in the film, and the respective band bending in the substrate/film structure are determined assuming a n-p junction between n–CuInSe2 and p–CuISe3–Se0. Electronic properties of the three-phase junction substrate/film/electrolyte are deduced and the validity of the derived energy-band diagram of the junction in contact is discussed.