Properties of charge carrier transport in Au/Phenyl C₆₁ butyric acid methyl ester/Au structure

The properties of charge carrier transport through the Au/phenyl C61 butyric acid methyl ester/Au (Au/PCBM/Au) structure are studied by measuring DC currents passing through the structure at various temperatures and in the presence of an external electric field. Temperature- and field-strength dependent conductivities show that the energy band gap of the PCBM crystalline solid is 1.70 eV, and this value depends on the pressure during its preparation. There is a thermally activated process that controls the carrier mobility of this PCBM solid. We found out that its activation energy is influenced by the external electric field, and it increases with increasing field strength. The activation energy increases from 2 to 110 meV corresponding to a variation of the field strength from 50 to 1000 Vcm_-1. Theoretical calculation shows that the magnitude of the potential barrier for carrier transport through the structure increases only from 2 to 7meV in the same field strength range owing to the Schottky effect on the Au/PCBM interface. Therefore, the field-strength-dependent mobility plays a more important role than the Schottky effect on the carrier transport through the structure.