Physical properties in new molten polymer: nanointerfacial electronic states

Physical properties and electronic structure of new molten conducting polymer, poly(2,5-dialkoxy-1,4-phenylene-alt-2,5-thiophene) (ROPPT) are investigated. The electronic states of ROPPT exhibit remarkable changes at the solid-liquid phase transition. Thermochromic behavior observed in ROPPT is a little different from that of poly(3-alkylthiophene) (P3AT), which is discussed by taking differences in molecular structures into account. The interfacial electronic energy diagrams of conducting polymer/metal interfaces were evaluated by the photoelectron spectroscopy. The shifts of the vacuum level were observed at all the measured interfaces and could be expressed as a linear relationship of the work function of the metal, showing the formation of an interfacial electric dipole layer. For good understanding of the properties of the organic electronic devices such as electroluminescent devices and organic photovoltaic cells, it is extremely important directly to clarify the interfacial electronic structures by a non-contact technique such as photoemission spectroscopy.