Observation of unusual, highly conductive grain boundaries in high-mobility phase separated organic semiconducting blend films probed by lateral-transport conductive-AFM

The effect of grain boundaries in high hole mobility organic blend films of diF-TES ADT:PTAA is evaluated using conductive-AFM measurements revealing the presence of unusually conductive grain boundaries. The latter characteristic has not been reported previously for any other organic semiconducting film system and is believed to underpin the excellent and morphology-independent hole transport characteristics seen in these composite films.

Enhanced Electrical Percolation Due to Interconnection of Three-Dimensional Pentacene Islands in Thin Films on Low Surface Energy Polyimide Gate Dielectrics

The role of lateral interconnections between three-dimensional pentacene islands on low surface energy polyimide gate dielectrics was investigated by the measurement of the surface coverage dependence of the charge mobility and the use of conducting-probe atomic force microscopy (CP-AFM). From the correlation between the electrical characteristics and the morphological evolution of the three-dimensionally grown pentacene films-based field-effect transistors, we found that during film growth, the formation of interconnections between the three-dimensional pentacene islands that are isolated at the early stage contributes significantly to the enhancement process of charge mobility. The CP-AFM current mapping images of the pentacene films also indicate that the lateral interconnections play an important role in the formation of good electrical percolation pathways between the three-dimensional pentacene islands.

Nanoscale electrical characterization of semiconducting polymer blends by conductive atomic force microscopy (C-AFM)

For the first time local electrical characteristics of a blend of two semiconducting polymers were studied with conductive atomic force microscopy (C-AFM). The investigated mixture is potentially interesting as the active layer in plastic photovoltaic devices. Besides conventional topography analysis of morphology and phase separation, the internal structure of the active layer was investigated by observing the current distribution with nanoscale spatial resolution. Similar to force spectroscopy, current imaging spectroscopy was performed during scanning the sample surface. Different types of current-voltage (I-V) characteristics were extracted from the array of spectroscopic data obtained from each point of the scans, and local heterogeneities of the electric characteristic were determined and discussed.