Decoupling Critical Parameters in Large-Range Crystallinity-Controlled Polypyrrole-Based High-Performance Organic Electrochemical Transistors

Despite the importance of structure and properties in organic mixed conductors, there exist very few material systems where the effects of relative crystallinity, crystallite size, and doping concentration could be effectively decoupled, while the resultant organic electrochemical transistors exhibit excellent device performance and stability. The film crystallinity and doping concentration could be independently controlled by adjusting the stoichiometry of the connector versus the pyrrole monomer, leading to the effective modulation of mixed conductivities and electrochemical characteristics as confirmed by electrochemical impedance analysis, organic electrochemical transistor characterization, and moving front measurement. The comprehensive structural and functional analyses suggest that there exist two distinct domains: the low crystallinity domain where carrier concentration is well controlled and the high film crystallinity domain where ion mobility is finely tuned. We believe that our study can provide general insights into the structure and properties of polymeric mixed conductors as well as the design principles governing their applications to biochemical sensing, bioelectric recording, and stimulation devices with customized properties.