Photoabsorption and desorption studies on thiophene-based polymers following sulphur K-shell excitation

▶ Photon stimulated ion desorption (PSID) measurements at the S K-shell excitation energies were performed on three thiophene-based polymer films, following their NEXAFS spectra. ▶ For poly(thiophene) (PT) and poly(3-methylthiophene) (P3MT) it was found that the S 1s → π*, σ* (S-C) excitation produces S+ desorption efficiently, showing the importance of the resonant Auger process for breaking the C-S bond. ▶ In the case of poly(3-hexylthiophene) (P3HT) S+ desorption seems to be suppressed due to the orientation of 3-hexyl side-chains on the surface. ▶ Desorption ion yield curves for molecular fragments reproduce the photoabsorption spectrum, indicating that the indirect process is here predominant.