Heterojunction organic field-effect transistor (OFET) based on p-type copper phthalocyanine (CuPc) and n-type hexadecafluorophthalocyaninatocopper (F16CuPc) was demonstrated. The heterojunction OFETs can be operated in normally-on (depletion-accumulation) mode, which attributes to the existence of a new conductive channel at the interface of heterojunction. The new channel is originated from accumulation of electrons and holes induced by the interface dipole. Compared with the device with CuPc single layer, the double channel transistor displays improved field-effect mobility from 0.017to0.042cm2∕Vs, and threshold voltage shifts from −17to+19V. In addition, ambipolar electric characteristics have been observed from the heterojunction OFETs.

Ambipolar organic field‐effect transistors (OFETs) are produced, based on organic heterojunctions fabricated by a two‐step vacuum‐deposition process. Copper phthalocyanine (CuPc) deposited at a high temperature (250 °C) acts as the first (p‐type component) layer, and hexadecafluorophthalocyaninatocopper (F16CuPc) deposited at room temperature (25 °C) acts as the second (n‐type component) layer. A heterojunction with an interpenetrating network is obtained as the active layer for the OFETs. These heterojunction devices display significant ambipolar charge transport with symmetric electron and hole mobilities of the order of 10–4 cm2 V–1 s–1 in air. Conductive channels are at the interface between the F16CuPc and CuPc domains in the interpenetrating networks. Electrons are transported in the F16CuPc regions, and holes in the CuPc regions. The molecular arrangement in the heterojunction is well ordered, resulting in a balance of the two carrier densities responsible for the ambipolar electrical characteristics. The thin‐film morphology of the organic heterojunction with its interpenetrating network structure can be controlled well by the vacuum‐deposition process. The structure of interpenetrating networks is similar to that of the bulk heterojunction used in organic photovoltaic cells, therefore, it may be helpful in understanding the process of charge collection in organic photovoltaic cells.