Optically induced switch of the surface work function in TiO2/porphyrin–C60 dyad system

Abstract

The TiO₂/P–C₆₀60 (porphyrin–C₆₀ fullerene dyad) system has been investigated by surface photovoltage spectroscopy under steady state (in the Kelvin-probe arrangement) and under chopped light illumination (in the capacitor arrangement). In contrast to TiO₂ with adsorbed porphyrins (M-5-(4-carboxyphenyl)-10,15,20-tris(4-methylphenyl) porphyrin) and N3 (Ru(dcbpyH₂)₂(NCS)₂) molecules, the TiO₂/P–C₆₀60 dyad system can be switched by light between negative and positive surface charging depending on the photon energy. A mechanism involving the participation of a photoinduced intramolecular charge transfer state in the P–C₆₀60 dyad is proposed in order to explain the observed changes in the photovoltage.