Electronic properties of the organic semiconductor interfaces CuPc/C60 and C60/CuPc

We report on the electronic properties of the organic heterointerfaces between C-60 and copper phthalocyanine (CuPc), studied by means of photoemission spectroscopy and the Kelvin-probe method. We found both interfaces, CuPc/C-60 and C-60/CuPc, to be nonreactive with pronounced shifts of the vacuum level pointing to the formation of an interfacial dipole mainly on the CuPc side of the heterojunctions. The dipole values are close to the difference of the work functions of the two materials. Important interface parameters and hole-injection barriers were obtained. It is shown that the sequence of deposition does not influence the electronic properties of the interfaces.