Spin scattering at the interface formed between metallic Fe and Cu-phthalocyanine molecules is investigated by spin-polarized scanning tunneling spectroscopy and spin-resolved photoemission. The results are interpreted using first-principles electronic structure theory. The combination of experimental and theoretical techniques allows us to shed light on the role of hybrid interface states for the spin scattering. We show that Cu-phthalocyanine acts, via hybrid interface states, as a local spin filter up to room temperature both below and above the Fermi energy, E F . At the same time, the molecule behaves as a featureless scattering barrier in a region of about 1 eV around E F . Similar properties are found for both single molecules and self-assembled molecular layers, so that the acquired microscopic knowledge can be transferred to operating devices.

We review our recent work in the field of organic spintronics, and show that the spin-and time-resolved twophoton photoemission (STR-2PPE) technique can be used to obtain quantitative information about the spindependent properties of hybrid organic-inorganic interfaces, as well as about the spin-dependent transport in organic semiconductors. In addition, we present STR-2PPE measurements performed on the Co-copper phthalocyanine (CuPc) system at different temperatures to investigate the microscopic processes repsonsible for the spin-polarization decay in organic semiconductors and at interfaces with such materials. We found no significant temperature dependence of the spin-injection efficiency across the Co-CuPc interface as well as of the spin-polarization decay length in CuPc .