Energy-level alignment at interfaces between gold and poly(3- hexylthiophene) films with two different molecular structures

The electronic structures of the interfaces between Au and poly(3-hexylthiophene) (P3HT) films with two different molecular orientations and orderings were investigated using synchrotron radiation photoemission spectroscopy. We found that, depending on whether thermal treatment was used, the P3HT thin film adopts two different molecular orientations, parallel and perpendicular to the silicon substrate, which result in different values of the vacuum level shift and hole-injection barrier. Thus, the molecular orientation and ordering of the P3HT material strongly affect the energy level alignment at the P3HT/Au interface.