Ambipolar charge transport in organic p-p junction disclosed by field-effect transistor and diode

Organic p-p junction composed of oxotitanium phthalocyanine (TiOPc) and copper phthalocyanine (CuPc) was investigated by analyzing the corresponding field-effect transistors, which exhibited typical ambipolar transport characteristics. Electrons and holes were induced at two sides of junction interface, respectively, which formed a built-in electric potential of 0.47 V directed from CuPc to TiOPc and resulted in a high conduction deduced by diode measurements. These results implied that both electron and hole current could be accumulated and transported at junction interface determined by the difference of Fermi levels of two materials, which is independent on their conductance types.