Conformation, Molecular Packing, and Field Effect Mobility of Regioregular β,β‘-Dihexylsexithiophene

Abstract

Improved synthesis, charge carrier mobility, conformation, crystalline structure, and molecular packing of the regiochemically pure 4‘,3‘ ‘‘ ‘-dihexyl-2,2‘;5‘,2‘ ‘;5‘ ‘,2‘ ‘‘;5‘ ‘‘,2‘ ‘‘ ‘;5‘ ‘‘ ‘,2‘ ‘‘ ‘‘-sexithiophene (β,β‘-DH6T) are reported. The sum of charge carrier mobilities of β,β‘-DH6T measured by the pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) technique was found to be ∑μmin = 3.9 × 10-3 cm2 V-1 s-1, which is comparable with the PR-TRMC mobility found for α,ω-DH6T. The field-effect mobility (FEM) of β,β‘-DH6T was found to be on the order of 10-5 cm2 V-1 s-1, which is considerably less than the FEM of α,ω-DH6T. To understand the reason for such poor macroscopic electrical properties, the conformation and the molecular packing of β,β‘-DH6T were systematically studied by means of UV−vis spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray techniques. Absorption spectra of a β,β‘-DH6T spin-cast film indicate the planar conformation of the aro...