No abstract

Photoelectron spectroscopy in the core level as well as the valence band region has been used to determine the electronic properties of interfaces between manganese phthalocyanine (MnPc) and the strong electron acceptor F 6 TCNNQ. It is shown that charge transfer occurs at this interface which results in the oxidation (reduction) of MnPc (F 6 TCNNQ) at the interface. Our data indicate a full electron transfer with no evidence for hybrid states. The valence band data suggest that the interface remains insulating/semiconducting despite the charge transfer, which indicates localized charges.

Manganese phthalocyanine (MnPc) is a member of the family of transition-metal phthalocyanines, which combines interesting electronic behavior in the fields of organic and molecular electronics with local magnetic moments. MnPc is characterized by hybrid states between the Mn 3d orbitals and the π orbitals of the ligand very close to the Fermi level. This causes particular physical properties, different from those of the other phthalocyanines, such as a rather small ionization potential, a small band gap and a large electron affinity. These can be exploited to prepare particular compounds and interfaces with appropriate partners, which are characterized by a charge transfer from or to MnPc. We summarize recent spectroscopic and theoretical results that have been achieved in this regard.

We have used photoelectron spectroscopy to determine the energy-level alignment at organic heterojunctions made of manganese phthalocyanine (MnPc) and the fullerene C60. We show that this energy-level alignment depends upon the preparation sequence, which is explained by different molecular orientations. Moreover, our results demonstrate that MnPc/C60 interfaces are hardly suited for application in organic photovoltaic devices, since the energy difference of the two lowest unoccupied molecular orbitals (LUMOs) is rather small.