Solvation induced morphological effects on the polymer/metal contacts

Polymer/metal interfaces play an important role in determining the performance of polymer based electronic devices. For most polymer diodes, one of the polymer/metal contacts is usually formed by spin casting a polymer solution onto a metal electrode; we call it polymer-on-metal (POM) contact. The other polymer/metal contact is usually formed by vacuum deposition of metal vapor onto the polymer surface; we call it metal-on-polymer (MOP) contact. In this article, we present evidence that the formation of the POM contact is strongly influenced by the processing of polymer thin films. The POM contact has a greater energy barrier for carrier injection than the MOP contact. The morphology of the polymer thin films, i.e., the relative arrangements of the side groups and conjugated backbone, significantly affects the interfacial characteristics. We also present a simple method of evaluating the morphological effects at the contact.