Optical studies on the mechanism of electrical conduction of doped polyacetylene

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Abstract
Optical spectra are measured with the AsF5 and Br2 doped polyacetylene films. By the doping, the π → π band located in the 19000 cm−1region is disappeared, while the new bands are observed at 870, 1370 and 5000 cm−1 regions. In addition, other new absorption bands are found around 570 − 660 cm−1 region by decreasing the temperature of the doped thin films, which may be assigned to the transitions between the levels of the electron-hole pair. The reflection spectrum of the AsF5 doped film shows a metallic behavior and it is analysed assuming a presence of free carrier. The conductivity estimated by the optical data is in good agreement with the measured one. The reflectivity of the bromine doped film is less metallic presumably because the chemical reaction may take place. The logarithm of the conductivity shows T−1/4 dependence, indicating that the conductivity is dominated by the hopping of the carrier between the chains.