Charge carrier generation, transport, and trapping in a photoconductive conjugated polymer: Polyphenylacetylene

Dark currents and photocurrents were measured in 3-6-μm-thick films of polyphenylacetylene (PPA) and of iodine-doped PPA. In undoped PPA, Schottky-Richardson injection from the electrodes is observed and holes are strongly trapped. Defect states exert a major control over dark currents and photocurrents. The photoconductivity action spectrum shows a good response in the red at energies well below the absorption edge. We conclude that undoped PPA is capable of trap-modulated electron transport through states in the band gap. Doping with iodine enhances photocurrents through charge transfer interaction.