Solid-state optical and electrical properties of new chiral oligothiophenes: the central role of supramolecular organization

Thanks to the possibility to modulate electronic and optical properties, organic semiconduc¬tors based on -conjugated polymers and oligomers have opened the way to the development of innovative optoelectronic devices. Their fundamental electro-optical properties (charge and exciton transport, light absorption and emission, response to external stimuli, etc.) depend not only on their chemical structure and the conformation assumed, but also on the supramolecular interactions and the nano/mesoscale organization in the solid-state.1 Chirality represents one of the most sophisticated expedients to control the supramolecular aggregation of similar systems (in particular their interchain spacing and/or alignment).2 As a further bonus, chiral - conju-gated systems may be used as active layers in sensors able to discriminate enantiomers3 or in circularly polarized (CP) light detectors4. We decided to work with new oligothiophenes – which have well known applications in opto-electronics – functionalised with some inexpensive alkyl chiral groups derived from natural sources, seeking self-assembly properties, which would ensure supramolecular chirality and the onset of extraordinary optical and electrical properties.Herein we describe: i) the synthetic route developed for the preparation of these oligomers; ii) their spectroscopic characterization (UV-Vis, ECD, fluorescence) to investigate the supramolecular organization in thin films prepared by drop casting or spin coating; iii) pre-liminary studies of CP-light detection in organic field-effect transistors (OFETs) based on the most promising oligothiophenes as semiconducting layers