Photoinduced Polymerization of Small Molecules for the Formation of Organic Electronic Devices

The application of small self-organized molecular systems for the formation of soft and in situ electrodes with combined electrical and biochemical signals leads to new means of bridging the biology-technology gap. Such systems have seen increased attention over the past few years with their promise of entirely novel pathways for monitoring and augmenting biological function. In parallel, organic electrochemical transistors (OECTs) have become a standard tool in the field of organic bioelectronics as they can take full advantage of ion (biomolecule) injection from an electrolyte (or physiological system) to modulate the volumetric conductivity of an organic semiconductor channel. In addition, overall biocompatibility and synthetic tunability of the organic conductive polymers make OECTs ideal for interfacing with biological systems. In this work we have combined the burgeoning field of in situ formed organic electronic materials into an OECT platform by using light-assisted photocatalysis. Specifically, we used direct light excitation, as well as excitation of porphyrins, for the in situ photoinduced polymerization of conjugated oligomers. The conjugated oligomers, bis[3,4ethylenedioxythiophene]3thiophene sulfonic acid (ETE-S, <i>i.e.</i>, an EDOT-thiophene-EDOT trimer with a sulfonate ligand) and a variety of derivatives (ETE-CooNa and EEE-CooNa) were implemented, and the photoinduced polymer films were assessed by cyclic voltammetry as well as transistor output and transfer characteristics. The resulting OECTs exhibited excellent figures of merit (Transconductance, on/off ratio) with performance approaching PEDOT:PSS but with several advantages. We believe that these results pave the way for expanded in situ bioelectronics and even OECTs and similar component fully formed/fabricated in vivo.