Heavy atom substitution - A strategy for improving conductivity in conjugated polymers

Heavy heteroatom substitution is a strategy for tailoring crystalline packing, carrier mobilities, and optoelectronic properties of the poly(3-chalcogenophenes) (P3AEs). In this study, the structure-property relationship is explored between S, Se, and Te substituted P3AEs and how heteroatom substitution affects the integration of dopants. Two oxidants with were used to positively-dope the P3AEs: iron(III) chloride and iron(II1) p-toluene-sulfonate hexahydrate. We observe that the size of dopant anion affects the doping efficiency, topology, and morphology of the P3AEs depending on the heteroatom substituted. Outstandingly, poly(3-alkyltellurophene) dopes most efficiently greatly improving its conductivity at low doping concentrations. Moreover, polymers doped with iron(III) p-toluenesulfonate hexahydrate all had considerable improvements at lower doping concentrations. Lightly doped P3AEs could be favorably incorporated into transistors, photovoltaics, and thermo-electrics without compromising conductivity or causing unwanted side-reactions between excess dopant and other components of the device.