Electrostatic phenomena in π-conjugated Langmuir-Blodgett films on metal electrodes

The surface potentials of three kinds of pi-conjugated Langmuir-Blodgget (LB) films (octasubstituted palladiumphthalo-cyanine (PcPd), perylene-tetra-carboxyldiimide derivative (PTCDI-SPent and PTCDI-OEt)) deposited on Au electrodes were measured using a Kelvin-probe method in a dark vacuum vessel at various temperatures. It was suggested that excess electronic charges were transferred from the electrodes into these LB films until thermodynamic equilibrium was established at the metalo-interface and resulted in the formation of an electrostatic layer on the order of several nano meters. The interfacial electrostatic potential formed at the interface between PcPd and PTCDI-SPent layers was also measured at various temperatures. It was found that electrons were transferred from PcPd to PTCDI-SPent layers at the interface.