Modulated charge separation at tetraphenyl porphyrin/Au interfaces

A frequency and temperature dependent change of the sign of modulated surface photovoltage signals from metal-free tetraphenyl porphyrin (H2 TPP) Au junctions has been observed. The sign of the modulated photovoltage signal could be switched by using continuous (bias) illumination, while the sign depends on the wavelength of the bias light. The light induced modulation of the negative and positive charges in the H2 TTP layer can be interpreted in terms of internal photoemission of electrons from Au into H2 TTP and of hole escape after exciton dissociation at the H2 TPPAu junction.