The purpose of this study is to use the layer-by-layer assembly (LbL) method to investigate the incorporation of ultra-thin insulating films into organic electronic device architectures and to improve the understanding of structure-property relationships as applied to how nanoscale architecture affects device performance. Initially, reflective Fourier transform infrared (FT-IR) spectroscopy is used to quantify the degree of cross-linking in poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) polyelectrolyte multilayers with a change in their intrinsic ionic interaction (solution pH) and an increase in post-deposition heat-treatment temperature. The breakdown strength of these dielectric films is then analyzed as a function of their degree of cross-linking, layer morphology, and film thickness to determine their applicability for use in metallized polymer film capacitors. Similar efforts are then directed toward the incorporation of these dielectric layers into both semi-conducting and doped organic thin film transistors (TFTs). While a field effect is observed when using a semi-conducting active layer, an electrochemical effect involving water is responsible for a change in the conductivity of the active layer in doped organic TFTs (PEDOT:PSS secondary doped with ethylene glycol). Similar observations are also apparent when using a standard (less conductive)active layer, whether it is deposited by spin-coating or with LbL assembly, but their response upon exposure to different environments is unique.
University of Cincinati