Influence of UV radiation and ozone exposure on the electro-optical properties and nanoscale structure of P3OT films

The modification of the nanoscale morphology and electronic behavior as well as the mesoscopic optical properties of thin films of poly-3-octyl-thiophene (P3OT) has been studied as these films are irradiated by ultraviolet light (UV). Films of about 100 nm thickness were prepared by spin-casting a P3OT solution in toluene on glass substrates. The samples were characterized by non-contact scanning force microscopy (NC-SFM), and by optical transmission measurements for every cycle of UV irradiation. Our experimental technique allows us to perform a nanoscale study of precisely the same area of the sample in order to correlate the effect of UV irradiation to specific morphological variations rather than to variations of the statistical properties of the sample. In addition, the decrease of film thickness is measured and correlated to the observed variation of optical absorption.