Phototransport effects in polyacetylene, (CH)x

We have made the first comprehensive measurements of the photovoltaic and photoconductivity effects in polyacetylene in that we have extended the spectral range originally covered by Matsui and Nakamura 17] to include the visible region as well. The photovoltaic experiments were done on Schottky barrier junctions formed between AsF₅ lightly-doped p-type trans-(CH)_x and a low work function metal, the first junctions of this type to be produced in semiconducting polyacetylene. The observation of a photovoltaic response threshold at 1.48 eV provides the first definitive measurement of the single-particle band gap in trans-(CH)_x. In addition, we have found the existence of a peak at 1.35 eV in the photoconductivity spectrum of undoped trans-(CH)_x which may be due either to extrinsic sources or to thermal dissociation of a weakly bound Wannier exciton.