Correlation between interface-dependent properties and electrical performances in OFETs

One of the fundamental points in determining the electrical performances in organic devices is that, even though they are usually thought as macroscopic devices, their behaviour is strongly driven by interfacial phenomena taking place in the nano scale. The focus of this thesis is the realization and characterization of Organic Field effect Transistors (OFETs) with a particular interest for investigating the influence of the interfaces on the electrical performances of the devices. Indeed, the parameters which mostly influence the electrical behaviour can be divided into to groups: 1) Intrinsic parameters of the material, as molecular packing and island nucleation, where the interfacial phenomena are taking place in the inter-molecular and inter-island scale. 2) Structural properties of the device, where the role of the triple interface metal electrode/organic semiconductor/gate dielectric can, in fact, significantly dictate the electrical behaviour of the device. In conclusion, in this thesis we demonstrated that the electrical and optoelectronic performances of organic semiconductor based devices are strongly influenced on one side by the geometry and architecture of the device itself, on the other hand, by the structural and morphological properties of the employed materials, and that the nanosized interfacial volume between the different materials layers in the device often play a key-role for determining the final properties of the device. In other words, device behaviour is more affected by material boundaries than by intrinsic properties of materials.