Sexithiophene (6T) was deposited onto PTFE layers oriented by friction. The films were studied by polarized spectroscopy : UV-visible, IR absorption, and fluorescence. The nature of the surface and the deposition rate are shown to greatly influence the orientation of the molecules and the mesoscopic organization of the film. A quantitative analysis of the orienting influence of the PTFE substrate toward the structure of the molecular film is shown.