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

This paper reports that the Schottky junctions between low workfunction metals (e.g. Al and In) and doped semiconducting polymerpellets (e.g. polyaniline (PANI) microsphere pellet and polypyrrole(PPy) nanotube pellet) have been prepared and studied. Since Ag is ahigh work function metal which can make an ohmic contact withpolymer, silver paste was used to fabricate the electrodes. TheAl/PANI/Ag heterojunction shows an obvious rectifying effect asshown in $I-V$ characteristic curves (rectifying ratio $gamma = 5$at $pm $6,V bias at room temperature). As compared to theAl/PANI/Ag, the heterojunction between In and PANI (In/PANI/Ag)exhibits a lower rectifying ratio $gamma = 1.6$ at $pm $2,V biasat room temperature. In addition, rectifying effect was alsoobserved in the heterojunctions Al/PPy/Ag ($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.