Influence of device geometry in the electrical behavior of all organic ambipolar field effect transistors

Microcontact printing has been used for realizing all organic, highly flexible, ambipolar field effect transistors based on a pentacene-C60 heterojunction. The contacts were patterned using poly(ethylenedioxythiophene): poly(styrenesulfonate) as conductive polymer. We have compared three different device architectures, bottom contact, top contact, and middle contact, and demonstrated in the last case that a perfect balance between n- and p-type mobilities may be obtained, being source ad drain directly interfaced with both semiconductors. This led to a significant improvement of the electrical performances, which, in turn, allowed the realization of all organic complementary inverters.