Photoemission study of the interface properties of aminothiophene derivatives in contact to Au as a function of conjugation length

The electronic properties of aminothiophene/gold interfaces have been investigated by photoemission spectroscopy in dependence of the amonithiophene conjugation length. The valence band onset as a measure for the charge injection barrier at these interfaces as well as the ionization potential depend on the length of the conjugated thiophene chain while the value of the interface dipole hardly varies. These results are discussed on the basis of recent theoretical approaches that aim to explain the interface dipoles.