Inkjet printing of organic transistor devices

In the last two decades inkjet printing passed from the field of graphic art and newspaper industry to that of organic and flexible electronics, as a manufacturing tool, becoming a major topic in scientific research. The appeal of this kind of technology is mainly due to its low cost, non-contact and additive approach, which makes it surely the most promising technique over the other technologies of Printed Electronics. The focus of this thesis is the optimization of the printing process, employing a piezo- electric Drop-on-Demand inkjet printer, for the realization of organic transistors on highly flexible plastic substrates, and their development in more complex systems for sensing applications. Indeed, all the devices realized have been investigated by means of electrical measures and spectroscopic techniques, in order to assess their performances and, consequently, to evaluate the reliability of inkjet printing as fabrication technique for such devices. In the first chapter a general introduction to the field of Printed Electronics, with particular focus on inkjet printing technique, is given. The second chapter provides informations concerning the fabrication characterization procedure followed, including a detailed description of the inkjet printing technology used, a report about the main physical and chemical properties of the materials employed, the explanation of the inkjet printing procedure for each material used in this thesis (as the printing parameters optimization and the approach for the resolution of some technical issues); finally also a brief description of the experimental techniques employed in order to characterize the devices is given. The third chapter is fully dedicated to the results concerning the fabrication and the characterization of all-Organic ElectroChemical Transistors (OECTs), while in the fourth chapter the results about inkjet printed Organic Field Effect Transistors (OFETs) are discussed. Finally, a brief chapter reports a summary of the main results achieved.