ABSTRACT

Polythiophenes have received a remarkable degree of attention as semiconducting polymers since their first use in the late 1980s [1, 2]. Their π-conjugated backbone allows efficient delocalization of electrons, affording a variety of self-assembled structures that find uses in organic field effect transistors (OFETs) [3], photovoltaics (OPVs) [4], light-emitting diodes (OLEDs) [5], radiofrequency ID tags (RFID) [6], biomedical devices [7] and sensors [8]. The ease of synthesis of polythiophenes compared to new, more complex polymeric structures has turned these polymers into a key workhorse system to study fundamental process–structure–property relationships. As a new paradigm in electronics device manufacturing develops to enable low-cost, large-area, flexible electronic devices, the ideal conjugated polymer must be either solution or melt processable to enable printed roll-to-roll processing [9]. As polythiophenes are known to thermally degrade when exposed to high temperatures, the solution processability route is often leveraged to deposit polythiophene based thin films [10, 11]. In which case, polymer solubility plays an important role in the ink formulation process. While polythiophene itself is insoluble, the addition of long, flexible hydrocarbon chains enhances the solubility and thus processability of this class of conjugated polymers [12, 13].