Structure-Electrochemical Property Relationship of F vs 2F Substituents in Low Bandgap Conjugated Polymers

Two alternating copolymers bearing fluorinated benzothiadiazole as a strong acceptor unit and dithienopyrrole as a strong donor unit were designed and synthesized to discuss the effect of the number of fluorine atom substitution. The polymers were characterized via cyclic voltammetry, spectroelectrochemistry, electrochemical impedance spectroscopy and galvanostatic charge discharge studies. Besides a red shift in absorption spectra, an anodic shift was also observed in the oxidation potentials when number of fluorine atom increases in the polymer backbone. Galvanostatic charge-discharge (GCD) studies revealed that difluorinated polymer exhibited enhanced area specific capacitance compared to mono fluorinated polymer.