Band Versus Hopping Transport in Conducting Polymers by Ab Initio Molecular Dynamics: Exploring the Effect of Electric Field, Trapping and Temperature

Abstract

AbstractUnderstanding charge carrier transport in conductive polymers is imperative for the materials' synthesis and optimizing devices. While most theoretical studies utilize time‐independent approaches for describing charge transport, there is an interest in addressing temporal charge carrier dynamics, which provides more information than time‐independent methods. In this study, ab initio molecular dynamics is utilized to gain microscopic insights into charge carrier temporal dynamics in PEDOT. It is demonstrated that transport along the chains is band‐like and across the chains is hopping‐like. Polaron mobility is calculated along the chains to be 4 cm2 V−1 s−1, providing a theoretical upper limit in thiophene‐based conducting polymers. Also, by tracing polaron jumps between chains, the hopping rate, aligning with Marcus' theory is extracted. If an electric field can release polarons from Coulomb traps is investigated, finding that the necessary field strength surpasses typical experimental values. Two regimes of intrachain polaron movement are found: under low/intermediate electric fields, polaron moves velocity‐constantly with coupled charge and lattice distortion, while under high electric fields, charge and lattice distortion decouple. The methodology applies to studying mobilities in p‐ and n‐doped conjugated polymers, including highly doped systems with more polymer chains, and incorporates dielectric screening to address the impact of shallow and deep traps.