The Relation Between Molecular Packing or Morphology and Chemical Structure or Processing Conditions: the Effect on Electronic Properties

Abstract

In the past few decades, mainly two kind of organic semiconductors, namely small molecules and polymers, have been dealt with. It turns out that the difference between these two categories in terms of charge carrier transport arises from the potentially different morphologies and the molecular packing. There are many studies showing the effect of the chemical structure on the electronic properties. However, in this study, the focus is on the role of processing conditions which is found to be of at least equal importance. To study a range of morphologies and packing in as similar molecules, two systems prepared by “Click”‐type chemistry are chosen, with the major difference between them being the replacement of a flat unit with one that introduces a slight twist to the aromatic skeleton. Through AFM and X‐ray studies, it is shown that the molecule with the potentially flat geometry can exhibit a high degree of π–π stacking, leading to morphologies ranging from polycrystalline to single crystals while the other is always in the amorphous film state. The transport properties are compared using organic field effect transistor (OFETs) in both top and bottom contact configurations.