Contact resistance in organic transistors: Use it or remove it

Abstract

The contact resistance of organic field-effect transistors is revisited to address its fundamental origin, parametric interplays, and technological implications. In a time when flexible electronics powered by an organic circuit comes close to the market, the revelation of wide-spread carrier mobility overestimation has astonished the broad scientific community, as this may contradict some of the most significant developments made to date. Since the contact resistance was pointed out as the major reason behind the issue, the research into reducing or eliminating this resistance has become more intense and justified than ever. However, there have been other revelations that suggest the benefits of contact resistance in certain structures and applications. Therefore, it seems timely to fairly judge the true meaning and consequences of the contact resistance, and to provide a comprehensive view covering both its positive and negative aspects, which constitutes the main motivation of this article. To maximize the depth of discussion, several important backgrounds for contact effects will be recapitulated before tackling selected practical problems of contact resistance, and before clarifying when it should actually be minimized and when it could otherwise serve as a useful element.