Optic Characterization of Oligo-Thiophene Multilayers

Abstract

Polythiophene is an interesting system for its remarkable charge transport and optical properties as well as for the investigation of the electronic excitations and their dynamics in one-dimensional structures. However, conformation and configuration defects in the real material result in physical properties depending on sample preparation and processing^1–3. On the contrary, thiophene oligomers are well-defined chemical systems with a precise structural definition of the condensed phase and provide considerable insight into the physical properties of polythiophene^4–6. Heteromultilayer organic structures represent one further step for the understanding of basic theoretical aspects such as the electronic level ordering and the dynamics of optical excitations. Considerable theoretical attention has been recently devoted to the linear and non-linear optical properties of organic multilayer systems^7–10. Besides the electronic properties of a single molecule the disorder present in the thin films leads to strong implications. It is, in fact, well kown that the optical and electrical properties of organic heteromultilayer structures are highly sensitive to the degree of structural order. Recently, it has been shown that highly oriented oligo-thiophene polycrystalline thin films can be grown by vacuum sublimation¹¹.