Berlin 2005 – scientific programme

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DS: Dünne Schichten

DS 4: Halbleitende, amorphe und organische Schichten

DS 4.3: Talk

Friday, March 4, 2005, 15:15–15:30, TU HS107

Energy level alignment at inorganic/organic interfaces: Si(111):H/ZnPc, F ₄ZnPc, F ₈ZnPc and F ₁₆ZnPc — •Thomas Mayer¹, Ulrich Weiler¹, Wolfram Jaegermann¹, Christian Kelting², Derck Schlettwein², Sergey Makarov³, and Dieter Wöhrle³ — ¹Institute of Materials Science Darmstadt University of Technology, D-64287 Darmstadt — ²Institute for Applied Physics Justus Liebig University Gießen, D-35392 Gießen — ³Institute of Organic and Macromolecular Chemistry, University Bremen, D-28334 Bremen

Interfaces of ZnPc and its F substituted derivatives on Si(111):H have been investigated with UPS and SXPS as model systems of a bulk composite absorber material for photovoltaic applications. Combining good absorptivity of dye molecules with good transport properties of Si is expected to result in high efficiency. A systematic variation of the energy level alignment at inorganic/organic interfaces is expected by substitution of an increasing number of hydrogen atoms of the organic molecule by fluorine atoms. Using calculated ionisation potentials, the HOMO energy levels are expected in the Anderson approximation at 0.6,1.0,1.3 and 1.7 eV below the valence band maximum of Si(111):H for ZnPc, F ₄ZnPc, F ₈ZnPc and F ₁₆ZnPc respectively. Combining SXPS and UPS we find the experimental HOMO levels at 0.45, 1.0, 1.0 and 1.55 eV respectively below the valence band maximum, mirroring the expected general trend. Interface dipoles are considered as the cause of the discrepancies to the Anderson line up. The consequences of the line up on expected charge transfer processes will be discussed.