Band bending in doped conducting polypyrrole: interaction with silver

Small amounts of silver were evaporated onto conducting polypyrrole films d oped by organic anions like tosylate or copper phthalocyanine trisulfonate. The electronic structure of these systems was studied by photoemission ele ctron microscopy, by photoemission spectroscopy and near edge X-ray absorpt ion spectroscopy. This investigation is an attempt to study the interaction of metallic contacts with organic semiconductors. A shift of the secondary electron onset in the valence band spectra was observed. This shift is cau sed by the neutralization of positive surface charges by an electron transf er from silver. We conclude that a natural band bending exists in pristine polypyrroles. We determine the hat band situation and describe the electron ic structure in a band-model scheme. (C) 2001 Elsevier Science B.V. All rig hts reserved.