Abstract.
C60 layers on polycrystalline Ag and Au are studied by photoelectron spectroscopy. At these metal/C60 interfaces an electron transfer occurs from the metal to the lowest unoccupied orbital of C60. We found in the case of the polycrystalline Ag/C60 interface a dipolar layer with its associated electric field in the direction corresponding to the charge transfer, so pointing from the substrate to the adsorbent. Yet, at the Au/C60 interface we observed an overall electric field pointing from C60 towards the metal. We discuss our observations in terms of charge transfer, screening and hybridization effects and propose the occurrence of a hybridization mechanism similar to back-bonding at the Au/C60 interface. We show that the alignment of energy levels at the metal/C60 interface cannot simply be deduced using the metal workfunction and the frontier orbitals of C60, including screening effects, since hybridization effects may strongly alter the interfacial energy level structure. Our experimental findings on the polycrystalline metal/C60 interfaces indicate an at-most weak dependence of the Fermi level of the C60 overlayer on the workfunction of the polycrystalline metal substrate. These interfaces are found in donor–acceptor-based organic photovoltaic devices and our results may help to understand the electrical characteristics of these devices.
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Received: 26 September 2001 / Accepted: 15 January 2002 / Published online: 3 June 2002
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Veenstra, S., Heeres, A., Hadziioannou, G. et al. On interface dipole layers between C60 and Ag or Au . Appl Phys A 75, 661–666 (2002). https://doi.org/10.1007/s003390201311
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DOI: https://doi.org/10.1007/s003390201311