Sulphur bridged [22]annulene[2.1.2.1] based organic field-effect transistors: interplay of the steric bulk and charge transport

Abstract

New, neutral, slightly puckered aromatic meso-substituted tetrathia[22]porphyrin[2.1.2.1] (TTP) macrocyclic architectures display structure dependent p-type semiconductor behaviour and constitute molecular field effect transistors with a high on/off ratio (1 × 10⁶) and high mobility (0.32 cm² V⁻¹ s⁻¹) in thin films deposited on octadecyltrichlorosilane (OTS) modified SiO₂. In order to study the influence of steric bulk, molecules with an increasing steric bulk at the meso-position have been synthesized and studied both experimentally and theoretically. The charge transport behavior was evaluated from their thin film organic field-effect transistor (OFET) devices. Single crystal analysis and thin film morphologies of the molecules showed that incorporating a branched hydrocarbon group at the meso-phenyl substituents of TTP not only alters face to face stacking patterns but also changes the morphology of the thin films from highly crystalline to amorphous, as well as lowering the solubility in organic solvents. Such features lead to deterioration of the performance of the organic semiconductor (OSC) devices.