Recombination kinetics of polarons in films of alkylator-sensing co-polymers

We report on the effect of an alkylating agent sensing of a nucleophilic unit, Pyridine-Thiophene (PyTh), on the polaron recombination in a co-polymer [Poly(3-hexylthiophene)]n(PyTh)m (m≈0.025nm≈0.025n). We show that by exposing the co-polymer to an alkylating agent, such as methyl iodide, the recombination rate increases substantially, possibly due to the introduction of additional recombination pathways created by the charge transfer between the electron deficient alkylated pyridinium sites and the electron rich thiophene polymer backbone.We also establish the bi-molecular-dispersive nature of the polaron recombination mechanism by following the modulation frequency and excitation intensity dependencies of the polaron photoinduced absorption.