Ambipolar charge carrier transport in mixed organic layersof phthalocyanine and fullerene

Mixed layers of copper-phthalocyanine ( p -conductive) and fullerene ( n -conductive) are used for the fabrication of organic field-effect transistors (OFET) and inverters. Regarding the electrical characteristics of these donor-acceptor blends they show ambipolar charge carrier transport, whereas devices made from only one of the materials show unipolar behavior. Such mixed films are model systems for ambipolar transport with adjustable field-effect mobilities for electrons and holes. By variation of the mixing ratio it is possible to balance the transport of both charge-carrier types. In this paper we discuss the variation of mobility and threshold voltage with the mixing ratio and demonstrate ambipolar inverters as a leadoff application. The gained results were analyzed by simulations using an analytical model for ambipolar transistors and subsequently compared to complementary inverters.