Mixed Ion-Carrier Diffusion in Poly(3-hexyl thiophene)/Perchlorate Electrochemical Systems

Abstract

The electrochemical reduction and oxidation of pi-conjugated materials is a ubiquitous characterization tool involving the process of mixed ion-carrier transport. The kinetics of this process is important to an array of technologies, but the underlying fundamental mechanisms remain a subject of contemporary debate. We present the results from in situ infrared spectroscopy and cyclic voltammetry (CV) that characterize the uptake of perchlorate ions into thin films of poly(3-hexyl thiophene) (P3HT). Given a set of easily satisfied conditions, the charging and discharging dynamics in both measurements can be almost exhaustively characterized by a single, voltage-dependent diffusivity describing the movement of ClO4–/hole polaron pairs. This study establishes the P3HT/ClO4– system as a mechanistically characterized benchmark to which other systems may be compared and highlights the importance of ion diffusion in the CV of pi-conjugated polymer films.