Mössbauer study of FeCl3-doped polythiophene and poly(3-octylthiophene)

We have specified the chemical species of the dopants in FeCl 3 -doped polythiophene and poly(3-octylthiophene) through 57 Fe-Mossbauer study as FeCl 4 - with slightly distorted tetrahedral structure. Spectra with a quadrupole-split doublet were observed for polythiophene, while those for poly(3-octylthiophene) were broadened by magnetic relaxation. Application of a magnetic field induced magnetically split spectra in both polymers due to a suppression of the relaxation frequency. In these conducting polymers there exist two kinds of chemical species with different relaxation frequency. The relaxation in poly(3-octylthiophene) is considerably slower than in polythiophene. The relaxation mechanism is attributable to the interaction between dopant spins and carrier spins.