Transient picosecond photoconductivity in polyacetylene

We present the results of transient photoconductivity measurements on highly oriented trans-polyacetylene. Using a photoconductive switching method utilizing picosecond optical pulses we have improved the temporal resolution of the photoresponse by one order of magnitude. We observe a fast temperature-independent photocurrent, which decays within a few picoseconds and reflects the intrinsic motion of charge carriers along the chains. Estimation of the mobility yields values of the order 1 ${\mathrm{cm}}^2$/V s, in good agreement with theoretical calculations. By comparison of the data to that obtained from recent transient photoinduced midgap absorption experiments, we conclude that the fast photocurrent is mainly due to polarons.