SPECTROELECTROCHEMICAL OBSERVATION OF POLY(BENZO[C]THIOPHENE) N-DOPING AND P-DOPING

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 +1.4 V. 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 lambda > 700 nm; 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.