AVS 52nd International Symposium
    Thin Films Monday Sessions
       Session TF+EM-MoM

Paper TF+EM-MoM8
CuPc:C60 Blend Film: A Photoemission Investigation

Monday, October 31, 2005, 10:40 am, Room 306

Session: Thin Films for Photovoltaic and Energy Applications
Presenter: L. Lozzi, University of L'Aquila and INFM-CNR, Italy
Authors: L. Lozzi, University of L'Aquila and INFM-CNR, Italy
V. Granato, University of L'Aquila, Italy
S. La Rosa, Sincrotrone Trieste Scpa, Italy
S. Santucci, University of L'Aquila and INFM-CNR, Italy
Correspondent: Click to Email
Recently a strong research effort has been devoted to study the application of organic-inorganic multiplayer films for the preparation of photovoltaic devices. Generally these devices are composed by a multilayer of an organic film which is the active layer, a charge acceptor (to reduce the electron-hole recombination probability) and the two metallic contacts to collect the charges (as ITO, Au and Al). The most used compounds are Copper Phthalocyanine (CuPc), as organic layer, and the C60, as electron acceptor. An improved system, showing an higher efficiency, can be prepared depositing, between the metallic contacts, a blend of active layer and charge acceptor. With this design one of the most important parameter, the exciton diffusion length (which is quite small in the organic systems), becomes less important because it is obviously much higher then the CuPc-C60 distance when these molecules are bonded. The realization of these blend films determines the strong reduction of the luminescence of the CuPc film, but it is not clear if in this blend film there is the formation of bonds between CuPc and C60 molecules or if its electronic structure is simply the sum of the electronic states of the two single compounds. In this contribution we will show the results obtained using soft X-ray photoemission spectroscopy on CuPc:C60 blend films, with different concentrations. These films have been deposited in ultra high vacuum by thermal evaporation. We will show a variation of the HOMO states as a function of the concentration ratio. This HOMO level moves towards the Fermi level, influencing the interface properties with the metallic contacts. The intensity and position of this level is strongly influenced by the CuPc:C60 ratio. This result could be related to the variation of the optical properties of these films.