Ambipolar organic field-effect transistors based on CuPc and F16CuPc: Impact of the fine microstructure at organic–organic interface

Ambipolar organic thin film transistors were fabricated by using hexadecahydrogen copper phthalocyanine (CuPc) and hexadecafluoro copper phthalocyanine (F16CuPc) as p-and n-type semiconductors, respectively. Ambipolar transport was observed in thin films based on either heterojunction (CuPc/F16CuPc or F16CuPc/CuPc with CuPc and F16CuPc as first deposited layer, respectively) or blend (CuPc:F16CuPc) architectures. Structure and morphology of thin films have been studied by atomic force microscopy (AFM) and X-ray diffraction (XRD). A careful study of the fine microstructure formed at the interface between CuPc and F16CuPc highlights the presence of three intermediate phase layers ensuring a continuously grown between highly ordered CuPc and F16CuPc polycrystalline thin films. Due to a better distribution between the phases (CuPc, F16CuPc and the intermediate phase layers), CuPc/F16CuPc heterojunctions give rise to an optimized ambipolar transport.