Supramolecular architecture and electrical conductivity in organic semiconducting thin films
Organic thin films are an essential component of the structure of optical and electronic devices. However, the optical and electrical properties of these films depend on their supramolecular architecture, which may vary according to the techniques used to manufacture them. Here, it was investigated the correlation between conductivity and supramolecular architecture. The supramolecular architecture was analyzed in terms of the molecular organization and J- or H-aggregation established during the fabrication of PTCD nanometric films. Three deposition techniques, such as Langmuir-Schaefer (LS), Langmuir-Blodgett (LB), and Physical Vapor Deposition (PVD), were evaluated. The UV-Vis absorption spectrum indicated that LS, LB, and PVD films grew homogeneously. Also, it was observed the presence of J and H aggregates for all films, prevailing the H aggregates for the LB film. The FTIR measurements suggested the molecular organization is similar for LS and LB films, with a tendency to form a head-on organization onto a solid substrate. For the PVD film, the perylene macrocycles are inclined approximately 45° relative to the substrate. AFM measurements indicated a homogenous surface for all films. In terms of electrical conductivity, the highest conductivity was found for LS, followed by LB and PVD. Conductivity values were interpreted in terms of molecular organization and J- or H-aggregate formation.