Impact of backbone fluorination on nanoscale morphology and excitonic coupling in polythiophenes

Significance Conjugated polymers (CPs) are some of the most attractive organic semiconductors for flexible optoelectronic device applications. The structural and optoelectronic properties of CPs are dependent on both the conformation of individual polymer chains and interactions between chains. Chemists have sought to control these interactions by creating more planar polymers that can pack tightly together and share strong electronic interactions. Single-molecule spectroscopy (SMS) studies of a fluorinated CP show that backbone fluorination does, in fact, lead to more planar polymer chains and highly ordered aggregates. Interestingly though, the electronic interactions are found to extend along individual chains rather than between chains. The studies demonstrate how SMS can test hypotheses about structure–property relationships in large molecular systems.