(Invited) Design and Fabrication of Organic Thin Film Transistors Using Solution-Processable Liquid Crystalline Phthalocyanine Derivatives

Abstract

Phthalocyanines (Pcs) are an extremely non-toxic organic chromophores with a range of versatile range applications from industrial pigments to photodynamic agents in cancer therapy and photosensitizers in photocopiers and compact discs. The central atom is coordinated with four pyrrolic nitrogen atoms. The conjugated π-systems of eighteen electrons in the macrocyclic ring gives rise to unique semiconducting properties which can be tuned by substituents of alkyl, alkoxy, or alkoxymethyl chains at sixteen sites on the benzenoid rings and axial ligation sites at the central metal or metalloid. Unsubstituted Pcs are generally both thermally and chemically stable but ring substituents such as SO3H and aliphatic chains confer solubility in water and organic solvents, respectively. They can form liquid crystalline phases. The present talk will highlight the achievements in application of phthalocyanine layers in different electronic devices such as field effect transistors (OFET) and memory devices taking into account literature data and our experimental results. Special attention will be focused to liquid crystalline phthalocyanines. Disk-like molecules, typically comprising a flat rigid aromatic core and flexible peripheral substituents, self-organizes into one-dimensional "supramolecular wires". Due to high charge carrier mobility along the columns, discotic mesogens are considered as realistic candidates for application in organic electronic devices. The well-ordered films with controllable molecule alignment can be obtained by slow cooling from isotropic liquid temperature.