Contact effects in organic thin film transistors with different device structures

In this work we discuss the contacts effects in organic transistors with different architectures (staggered and coplanar). By using electrical measurements, performed at different temperatures, and numerical simulations, we show that electrical characteristics of both types of devices can be reproduced considering an effective Schottky barrier and barrier lowering at the source contact. Furthermore, we show that in staggered devices, at low Vds, the current is injected along an extended source contact region, while at high Vds is mainly injected at the edge of the contact, as for coplanar devices. The different architecture also results in different voltage drop at the contact for different drain bias. These differences explain the different contact resistance observed for the two device architectures.