Dissipative charge transport in organic mixed ionic-electronic conductor channels

Understanding charge transport in organic mixed ionic-electronic conductors (OMIECs) is crucial to improve the performances of bioelectronic and neuromorphic devices. Recent studies reveal that the amplification of electrical signals in organic electrochemical transistors is determined by the volumetric capacitance c_v and electronic mobility μ_e of OMIEC channels, but how material parameters impact on the signal propagation speed and energy dissipation remains unclear. To address this issue, we combine electrical measurements of the phase velocity in microstructured OMIEC channels with local measurements of ionic displacements with modulated electrochemical atomic force microscopy. We interpret experimental data with a simplified transmission line model to determine the dispersion relation for OMIEC channels. We demonstrate that at relevant frequencies the phase velocity is dominated by the ratio of μ_el/c_v, constituting an additional figure of merit to benchmark material formulations. These results highlight intrinsic limitations of OMIEC-based circuits and compare their efficiency with neuronal signal transmission.