Barrier heights of polymer-electrode interfaces measured via photo injection current method

Abstract

The metal-polymer contact interface plays a major role in the conduction and breakdown process in flexible dielectrics. Enhancing barrier heights has been investigated for effectively blocking the charge injection and thus impeding the degradation of the dielectrics in the field. However, the electronic band structure at the metal-dielectric interface and its relationship with the electrical insulation properties are still not well understood due to the complex morphological details of the interfacial region. Here, we determine the barrier height profiles of various sets of metal electrodes and dielectric polymers systems by utilizing the photo injection current method. Our results reveal that all aromatic polymers tend to have lower barrier heights than aliphatic polymers, and thus we believe that the chemical structure plays a prominent role in determining the barrier heights. Additionally, an important trend for aromatic polymers/metal configurations has been found that those aromatic polymers with higher glass transition temperatures feature however lower injection barrier heights. The correlations uncovered in this work unveil an effective approach of rational modifying the chemical structure to build polymers that can efficiently block charge injection for reliable insulation performance at elevated temperatures.