The electronic structure of organic charge injection layer/ metal interfaces studied with photoemission spectroscopy and scanning probe microscopy
The electronic structure of metal-organic interfaces incorporated in organic electro-optic and optoelectronic devices, e.g., organic light emitting diodes and photovoltaics, is important in determining some of the critical device operating parameters such as power efficiencies, and threshold and operating voltages. The interfacial electronic structure depends on the nature of the interactions between the organic material and the metal, which can be roughly divided into two groups: electrostatic and chemical interactions. The electrostatic interactions result in the rearrangement of the electronic charge within the near-interface layer of the organic, which may, in some cases, depend on the organic film crystal structure. The chemical interaction, on the other hand, depends on the chemical reactivity of the metal and the organic material, and may involve the formation of metal–organic charge transfer complexes, or bond breaking and making giving rise to new species. By carefully selecting the components of metal – organic interfaces we have been able to study the interfacial electronic structure both in the presence and in the absence of chemical interactions.