Photoelectrochemical properties of a series of electrostatically self-assembled films based on sandwich-type polyoxometalates and a bichromophore hemicyanine dye

► Electrostatically self-assembled films from polyoxometalates and hemicyanine. ► Transition metals in polyoxometalates strongly affected large cathodic photocurrents. ► Bathochromic shift in the visible absorption band of the films.