Investigating the Mechanism of Post-Treatment on PEDOT/PSS via Single-Particle Absorption Spectroscopy

The conductive polymer poly­(3,4-ethylenedioxythiophene)–poly­(styrenesulfonate) (PEDOT/PSS), widely used in optoelectronic devices, exhibits improved conductivity upon post-treatment, but the mechanism of this improvement is difficult to fully ascertain. The effects of thermal annealing and dimethyl sulfoxide (DMSO) post-treatment on PEDOT/PSS, from the nano- to mesoscale, are studied using single-particle absorption spectroscopy. An average decrease in size and apparent increase in rotational order of individual particles are observed with both treatments, including unexpected correlations between change in rotational order and initial properties. Simulation of these transformations and correlations occurring during the annealing process reveals that the effects of DMSO post-treatment can be explained by oligomer depletion and do not explicitly require conformational changes including oligomer rotation.