Rectifying effect of heterojunctions between metals and doped conducting polymer nanostructure pellets

This paper reports that the Schottky junctions between low work function metals (e.g. Al and In) and doped semiconducting polymer pellets (e.g. polyaniline (PANI) microsphere pellet and polypyrrole (PPy) nanotube pellet) have been prepared and studied. Since Ag is a high work function metal which can make an ohmic contact with polymer, silver paste was used to fabricate the electrodes. The Al/PANI/Ag heterojunction shows an obvious rectifying effect as shown in I-V characteristic curves (rectifying ratio \gamma = 5 at \pm 6 V bias at room temperature). As compared to the Al/PANI/Ag, the heterojunction between In and PANI (In/PANI/Ag) exhibits a lower rectifying ratio \gamma = 1.6 at \pm 2 V bias at room temperature. In addition, rectifying effect was also observed in the heterojunctions Al/PPy/Ag (\gamma = 3.2 at \pm 1.6 V bias) and In/PPy/Ag (\gamma = 1.2 at \pm 3.0 V bias). The results were discussed in terms of thermoionic emission theory.