Abstract
A model mixed-conducting polymer, blended with an amphiphilic blockcopolymer, is shown to yield systems with drastically enhanced electrochemical doping kinetics, leading to faster electrochemical transistors with a high transduction. Importantly, this approach is robust and reproducible, and should be readily adaptable to other mixed conductors without the need for exhaustive chemical modification. New Concepts: Semiconducting polymers attract great interest for bioelectronics applications due to their soft nature and mixed ionicelectronic conduction capabilities. So far, most efforts focused on enhancing mixed-conducting functionalities by introducing polar side chains. Here, we show that blending offers a powerful, general approach to improve mixed conduction. We used a block copolymer of poly(3-hexylthiophene) and poly(ethylene oxide) (P3HT-b-PEO) as additive for a relatively poorly performing model material based on a random copolymer between 3-hexylthiophene and 3-(6hydroxy)hexylthiophene, (P(3HT-co-3HHT)), to unambigously demonstrate the benefit of our strategy. Blends and neat P(3HT-co-3HHT) show similar transduction performance when implemented in organic electrochemical transistors (OECT)s, yet, intriguingly, blends display drastically reduced drain-current hysteresis because of faster electrochemical doping; i.e., blends introduce ion-transporting pathways without negatively affecting the semiconductor's electronic conductivity. This is desired for electrochemical transducer operation and is rendered possible via use of the amphiphilic block copolymer that imparts hydrophilicity to the active layer and promotes partial miscibility between blend components, preventing the need of stabilizing the films by cross-linking. Additionally, a notable thresholdvoltage stability across gate-potential sweep rates and a low impedance is found, thanks to the electrolyte/redox-polymer compatibilization due to the presence of the additive, rendering these blends promising for numerous applications, including electrochemical biosensing.