Conjugated polymer surfaces and interfaces: A mini-review and some new results

Since the discovery of high electrical conductivity in doped polyacetylene in 1977, conjugated polymers have emerged as viable semiconducting electronic materials for numerous applications. In the context of polymer electronic devices, it is of critical importance to understand the nature of the electronic structure of the polymer surface and the interface with metals. It has been shown that, especially for conjugated polymers, photoelectron spectroscopy provides a maximum amount of both chemical and electronic structural information in one (type of) measurement. An overview of some details of the early stages of interface formation with metals on the surfaces of conjugated polymers and model molecular solids, especially in connection with polymer-based light-emitting diode (LED) devices, was presented at the symposium for Alan Heeger. Materials involved include poly(p-phenylenevinylene) (PPV), as well as a series of substituted PPVs, and a diphenylpolyene molecule, namely alpha,omega-diphenyltetradecaheptaene. Some general trends in the behavior of light-metal atoms on the clean surfaces of conjugated polymers was pointed out. Here, the core details of the oral presentation will be outlined. In addition, some new results presented are discussed, briefly, in order to indicate some recent new developments in this area. Finally, some details of one specific new issue are reviewed in slightly more detail. The choice of new results presented is influenced by recent publications by Alan Heeger and friends at Santa Barbara.