Surface and Interface Modified Thermal, Structural and Charge Transport Properties in Conjugated Polymer Thin Films

Conjugated polymers are widely employed as the active layer in various electronic and optoelectronic devices. In this article, the modifications of thermal, structural and charge transport properties of conjugated polymers confined in thin film geometry are reviewed. Deviations of thermal transition temperatures of conjugated polymers are summarized and discussed through lessons drawn from conventional saturated polymer thin films. These phenomena are explained by the surface and interface effects that virtually divide a thin film into several vertically heterogeneous layers each having different physical characters. The precise determination of thermal transition temperatures as a guide for rational thermal treatments of various devices is highlighted. We then review surface and interface mediated molecular structure in conjugated polymer thin films via surface- and bulk-sensitive techniques, e.g. near-edge X-ray absorption fine structure and grazing-incidence wide-angle X-ray scattering, and discuss how local morphology can affect charge mobility in the out-of plane and in-plane directions in diodes and field-effect transistors. A thorough understanding of these phenomena and the underlying mechanism is critical for the rational design and precise control of devices for high performance.