Modulation of electronic and ionic conduction in mixed polymer conductors via additive engineering: Towards targeted applications under varying humidity

Polymer solids with mixed ion and electron transport hold great promise for next-generation organic electronics, and rational regulation of ionic/electronic contribution within these materials can enable a broadened spectrum of practical applications. However, a fundamental understanding of the conduction mechanisms and their correlations with morphological characteristics remains limited, especially under varying environmental humidity conditions. In the present work, simple additive engineering enables the effective regulation of electronic and ionic contribution in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) based conductors, giving rising to ion- and/or electron-dominant conductions. As a demonstration, PEDOT:PSS films with different electrical characteristics are successfully applied for thermal energy harvesting, healthcare monitoring and human motion detection upon humidity exposure. Combining operando alternating current (AC) impedance spectroscopy and grazing incidence small-angle X-ray scattering at low and high humidity levels, additive-dependent charge transport mechanisms are elucidated, and correlations between morphological alterations and conductivity evolutions are revealed. This work achieves highly tailorable PEDOT:PSS conduction utilizing Zonyl, dimethyl sulfoxide (DMSO) and carbon nanotubes (CNTs) as additives with distinct humidity responses and gains an in-depth comprehension of underlying mechanisms, which are expected to pave the way for next-generation organic electronics.