IN-SITU ELECTRON-SPIN-RESONANCE STUDY OF N-DOPING AND P-DOPING OF POLYTERTHIOPHENE

Electropolymerized poly(terthiophene) (PTT) films on Pt electrodes hav e been studied using in situ electron spin resonance (ESR) spectroscop y. ESR spectra were acquired as a function of doping level for both p- and n-doping of PTT films exposed to tetraethylammonium tetrafluorobo rate/CH3CN solutions. Within the accessible potential range, the maxim um n-doping level is y approximate to 0.1, ca. 40% of the maximum p-do ping level. At low p- and n-doping levels, radicals are generated appr oximately linearly with injected charge, although the spin:charge rati o is substantially below unity Linewidths indicate these spins to be m obile. At high p-doping levels, the ESR signal intensity decreases and the linewidth increases; we interpret this in terms of metallic chara cteristics. Following p-doping, nominally undoped films contain trappe d radicals, which are removed on subsequent p- or n-doping. Throughout , g values indicate little or no participation of the heteroatom orbit als. For the thin films studied here no skin effects are observed.