Very Large Silacylic Substituent Effects on Response in Silole-Based Polymer Transistors

Abstract

Understanding the interrelationships between molecular structure and organic thin film transistor performance is key to the realization of novel organic semiconductors achieving superior device characteristics. Herein we report the synthesis, characterization, and charge-transporting properties in organic field-effect transistors (OFETs) of dithieno silole-based oligomers and copolymers having silacycloalkyl substituents. Silacyclization of the alkyl substituents on the silole silicon atom reduces steric encumbrance, contracts solid state intermolecular π−π contacts, and enhances the charge-transport capacity of the oligomers. Oligomer 3,3′-dihexylsilylene-2,2′:5,2′′:5′,2′′′:5′′,2′′′′:5′′′,2′′′′′-sexithiophene (SM5) with two Si-n-hexyl substituents is not FET-active, while the mobilities of 3,3′-cyclopentanylsilylene-2,2′:5,2′′:5′,2′′′:5′′,2′′′′:5′′′,2′′′′′′-sexithiophene (SM4) and 3,3′-cyclobutysilylene-2,2′:5,2′′:5′,2′′′:5′′,2′′′′:5′′′,2′′′′′-sexithiophene (SM3) FETs are 2.6 × 10−4 and 3.4 × 10−4 cm2/(V...