An OTFT based on titanium phthalocyanine dichloride: A new p-type organic semiconductor

A p-type organic thin film transistor (OTFT) was fabricated based on an axially-substituted phthalocyanine (titanium phthalocyanine dichloride: TiCl2Pc). Molecular energies and atomic charge distributions of a series of axially-substituted metal phthalocyanines were studied using measurements of their electrochemical properties and X-ray photoemission spectroscopy, respectively. Based on these measurements, the relationship between the charge carrier transport types of the phthalocyanines in OTFTs and their substituted groups (metal and axial ligands) are discussed. The axially-substituted electron-withdrawing groups can effectively lower the LUMO energy and increase the charge separation, contributing to the realization of n-type behavior, e.g. in SnCl2Pc. The electronegativity of the metal also affects the LUMO energies and charge distributions, such that TiCl2Pc is a p-type semiconductor.