Interface electronic properties of oligothiophenes: the effect of chain length and chemical substituents

We present a comparison of the energy levels at interfaces between different thiophene based organic semiconductors and gold. The thiophene materials are comprised of oligomers with different length and with additional saturated side chains. Our results demonstrate that the interface dipole at these interfaces is independent of the molecule length as well as of the substitution. In addition, the position of the Fermi level in the gap of the organic semiconductors indicates that these interfaces are not free from interactions.