Enhancement of the electrical conductivity of polypyrrole films on applying higher voltage

The effect of voltage on the conductivity of polypyrrole films has been investigated. It is found that the conductivity of the films increases with some structural change after the applied voltage reaches a higher value. The degree and the stability of the conductivity enhancement are related to the nature of the counter-anions doped in the polypyrrole films. A 65% increase in conductivity of the film doped with TsO− is observed on applying higher voltage, and it remains stable after the treatment. The conductivity of the film doped with NO3− increases 47% on applying higher voltage, but it drops back to its original value quickly after the higher voltage is turned off. The structural change of PPy(TsO−) is studied through Vis and NIR absorption spectra.