Matthew Waldrip, Oana Jurchescu,
Organic semiconductors have sparked significant interest due to their inherent properties as flexible, solution processible, and chemically tunable electronic materials. In the last 10 years, the improvements in charge carrier mobility in small molecule and polymer materials has put organic semiconductors in a competitive position for incorporation in a variety of (opto)- electronic applications. One example is the organic field-effect transistor (OFET), which is the fundamental building block of many applications based on organic semiconductors. While the performance improvements open up possibilities in applying organic materials as active components in fast switching electrical devices, the ability to make good electrical contact hinders further development of deployable electronics. At the same time, inefficient contacts represent serious bottlenecks in identifying new efficient electronic materials by inhibiting access to their intrinsic properties, or providing misleading information. Recent work to understand the complicated relationships of contact resistance with applied voltage, metal and dielectric interfaces, the broadened energetic states of organic semiconductors, and more, has led to a steady reduction in reported contact resistance in OFETs. While impressive progress has been made, contact resistance is still above the limits necessary to drive devices at the speed required for many active electronic components. This review covers current understanding of the origins of contact resistance and recent improvement in organic transistors, with emphasis on the electric field and geometric considerations of charge injection in field-effect transistors.
Advanced Functional Materials
organic electronics, contact resistance, transistors