Impact of Ionic Species on the Performance of Pedot:PSS-Based Organic Electrochemical Transistors

The organic electrochemical transistor (OECT) has received considerable interest in the field of bioelectronics due to its ability to support both ionic and electronic transport. However, the fundamental aspects of the OECT's operation are not yet fully understood. Here, the impact on the performance of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)-based OECTs, of a series electrolytes with chloride-based ions is evaluated, varying their cation counterpart under the extension of the Hofmeister Series. Electrical results are analyzed using the Bernards-Malliaras and Faria-Duong models and correlated with quartz crystal microbalance measurements. It is shown that cations with a higher ability of salting-in, according to the Hofmeister series, swell the channel with higher efficiency. In addition, cations with a higher ability to salt-out promote smaller modulations in the channel's current, indicating that the ionic transport in the bulk of the channel is directly correlated with the swelling ability of the film. Overall, the results provide a better understanding of the interplay of channel and electrolyte in OECTs and promote guidelines for optimizing materials choice for highly sensitive OECTs.