Absorption and Reflection Spectra of Pure and ClSO3H Doped Polyacetylene Films

Abstract

Optical absorption and reflection measurements are carried out on pure and ClSO₃H doped polyacetylene films over a wide wavelength region (350–35000 cm⁻¹). In the doped polymer, the transition from the valence band to the impurity level is observed at 870 cm⁻¹ and the free carrier absorption band appears over the wide region of 350 to 20000 cm⁻¹, while the interband transition located in the region of 15000 cm⁻¹ disappears. This means that doping removes the bond alternation leading to a uniform bond length and all π-electrons contribute to the transport. For the heavily doped films, the d.c. conductivity of polyacetylene films is obtained by the optimum fit of the theoretical curve to the observed absorption and reflection spectra. The obtained values are comparable with the d. c. conductivity (σ\simeq280–250 Ω⁻¹ cm⁻¹) obtained by the four probe method.