On the Nature of Charge Injecting Contacts in Organic Field-Effect Transistors.

Organic field-effect transistors (OFETs) are key enabling devices for plastic electronics technology, which has a potentially disruptive impact on a variety of application fields, such as health, safety and communication. Despite the tremendous advancements in understanding the OFET working mechanisms and device performance, further insight into the complex correlation between the nature of the charge injecting contacts and the electrical characteristics of devices is still necessary. Here, an in-depth study of the metal-organic interfaces that provides a direct correlation to the performance of OFET devices is reported. The combination of synchrotron x-ray spectroscopy, atomic force microscopy, electron microscopy, and theoretical simulations on two selected electron transport organic semiconductors with tailored chemical structures allows to gain insight on the nature of the injecting contacts. This multiple analysis repeated at the different stages of contact formation provides a clear picture on the synergy between organic/metal interactions, interfacial morphology and structural organization of the electrode. The simultaneous synchrotron x-ray experiments and electrical measurements of OFETs in operando uncovers how the nature of the charge injecting contacts has a direct impact on the injection potential of OFETs.