The electrical characteristics of organic thin-film transistors (OTFTs) are frequently affected by contact effects, which can seriously reduce the transistor performance. The importance of the contact resistance, R c , is more relevant in the case of high carrier mobility and/or small channel length devices, where its value may become comparable or even larger than the channel resistance. R c appears to be strongly affected by the device architecture, and much higher R c values are typically observed, at low-drain voltages, in coplanar structures (i.e., bottom-gate/bottom-contact (BGBC) devices) than in staggered structures (i.e., top-gate/bottom-contact (TGBC) devices). The presence of Schottky barriers, trap states, field dependence of carrier mobility, and defected regions near the electrodes has been suggested as the origin of R c …