Conductivity of Electropolymerized Thiophene Films: Effect of Fused-Ring Thiophenes as the Monomer

Polythiophene and its derivatives have emerged as promising candidates for next-generation electronic applications due to their tunable conductivity and ease of synthesis via electropolymerization. Although fused-ring thiophene monomers have attracted considerable interest for the fabrication of polythiophene films with enhanced electronic properties, systematic investigations comparing their conductivities and elucidating the structural influence of fused-ring motifs remain limited. In this study, we explore the electropolymerization behavior of various fused-ring thiophene monomers and systematically evaluate their conductivities through in situ electrochemical conductance measurements. Complemented by theoretical calculations of monomer aromaticity using nucleus-independent chemical shift (NICS) and multicenter bond index (MCBI) analyses, our findings reveal that the inhomogeneous aromaticity of fused thiophene rings plays a pivotal role in determining the conductivity of the resulting polythiophene films.