Spectroelectrochemical observation of poly(benzo[c]thiophene) n- and p-doping

Abstract

The deposition and properties of electropolymerised poly(benzo[c]thiophene)(PBCT) films have been studied using in situ UV–VIS spectroscopy. Film stability is enhanced by ‘conditioning’ in background electrolyte [0.2 mol dm^–3 tetraethylammonium tetrafluoroborate (TEAT)–CH₃CN]; this involves a single potential cycle between –0.5 and +1.4V. In addition to the previously reported p-doping process, we describe n-doping in 0.2 mol dm^–3 TEAT–CH₃CN. The level of n-doping is ca. two-thirds that of p-doping, and it occurs in a single stage, rather than the three stages seen for p-doping. The spectroscopic changes on p- and n-doping are broadly similar, except that the final stage of p-doping is accompanied by an increase in absorbance at λ > 700nm; no such change is seen during n-doping. The differences in the potentials required for p- and n-doping correspond to the energy of the main visible absorption feature for undoped PBCT.