Multi-length Scale Electrochemical Insights into Conducting Polymer Functionality using Scanning Electrochemical Cell Microscopy

Scanning electrochemical cell microscopy (SECCM) is an electroanalytical capability for investigating multi-length scale redox reactions in functional materials. This technique raster scans a sub-micron diameter electrolyte-filled capillary over electrode surfaces. This talk will focus on adapting SECCM to understanding fundamental semiconductor electrochemical phenomena of conducting polymers (CPs), with a focus on understanding the physiochemical origins of electrochemical heterogeneity and function to drive redox reactions.
CPs are highly scalable, printable, and have facile redox tuning through synthesis. The energetic landscape of CPs are complex, with contributions arising from interactions such as dynamic swelling, ion and solvent insertion, and chain entanglements. This local electrochemical landscape ultimately affects a polymer’s ability to selectively and efficiently drive redox reactions. Here, two polymers in the area of organic electronics have been considered: poly-3-alkylthiophene-2,5-diyl; P3HT and poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene]; PBTTT. Electroabsorption measurements are first used to investigate the collective electrochemically active density of states (DOS(E)). SECCM is then used to understand the multi-length scale structural impact on electrochemical functionality. P3HT has a flexible chain backbone which give rise to broad distributions in redox properties and slower rate coefficients. Alternatively, PBTTT demonstrates a narrow and more homogeneous distribution of DOS(E), attributed to the more planar conjugated backbone resulting in a faster set of rate coefficients. These multi-length scale insights highlight the strength of incorporating SECCM into electrochemical studies and how synthetic design can be leveraged to selectively drive redox reactions to advance polymer-based semiconductor functionality for (photo)electrochemical reactions.