Molecular surface structure of poly(3-hexylthiophene) studied by low energy ion scattering

Low energy ion scattering and X-ray photoelectron spectroscopy were used to study the surface of thin spin-coated poly(3-hexylthiophene) (P3HT) films on silica. We found that the composition of the outermost surface differs from that of the bulk due to the surface molecular structure: the sulphur atoms are screened from being at the outermost surface, presumably by the hexyl side-chains. The influence of this intramolecular segregation phenomenon on the composition is limited to the outermost surface. Comparison of the sputter-profile of P3HT with that taken on a polycrystalline α-quaterthiophene film shows that after sputtering the sulphur to carbon atomic ratio of bulk P3HT is observed.