Synthesis and Characterisation of Phosphonated PEDOT—An Organic Material for Energy-Efficient Bioelectronics

Abstract

Abstract Body: Conjugated polymers (CPs) have found great success as active materials in organic electrochemical transistors (OECTs), which can be integrated into bioelectronic devices for cell monitoring and stimulation.1,2 The success of CPs in this application is dependent on their material design: CPs must exhibit electrochemical activity in aqueous environments and support OECT operation in the energy-efficient, accumulation mode. Current materials such as PEDOT:PSS present several challenges, including depletion mode operation in OECTs, which is less energy-efficient; water solubility, which necessitates crosslinking or post-treatment;3 and high acidity, which can limit their biocompatibility with specific cell lines.4 Consequently, there is a clear need to develop new CPs for aqueous OECTs which overcome these limitations. To this end, we have synthesised and characterised a new CP, poly(ethylenedioxythiophene) functionalised with isopropyl-protected phosphonate groups (PEDOT-Phos). This material is readily processed in organic solvents, can be proton doped with non-oxidising acids, and exhibits reversible electrochemical activity in aqueous electrolytes. Most importantly, we used PEDOT-Phos as the channel material in aqueous, accumulation mode OECTs which boast low threshold voltages and high volumetric capacitances and transconductances, without requiring additives or post-treatments. Overall, PEDOT-Phos is a promising electronic material for applications in energy-efficient, organic bioelectronics.