Strange discharge current transients in polyethylene oxide

The polarization and the depolarization current after application of a voltage step are investigated in the solid electrolyte polyethylene oxide. For low applied fields the current density follows a Kohlrausch behavior, i.e. j α fα, in the long time range during the polarization and the depolarization process respectively. By using sufficiently high applied fields charge injection sets in and the current during the polarization process is nearly constant at long times. It turns out that the transient depolarization current in this case shows a pronounced unforeseen maximum. The time to the maximum as well as the height of the current peak depend on the field applied before, the polarization time, the temperature, the LiClO4 doping, the electrode material, and the sample length. Simulations carried out using a discrete three-dimensional hopping model reveal qualitatively comparable results. It is concluded that the injection and later extraction of excess electrons according to Lindmayer's theorem is responsible for the appearance of the current maximum.