The interface between phthalocyanines and PEDOT:PSS: evidence for charge transfer and doping

As model systems, differently fluorinated representatives from the family of phthalocyanines (CuPC, CuPCF4, and CuPCF16) with different ionization potentials were evaporated onto PEDOT:PSS (mixture of poly-3,4-ethylenedioxy-thiophene (PEDOT) and polystyrenesulfonate (PSS)) thin films, which are often applied as electrode material in (all-)organic semiconductor devices. The electronic interface properties were studied using both core and valence level photoemission spectroscopy. The alignment of the electronic levels of the phthalocyanines on PEDOT:PSS is compared to inert and reactive inorganic substrates. For reactive systems, the direction of the charge transfer depends clearly on both the ionization potential of the organic semiconductor and the work function of the substrate.