Transient Conductivity Measurements in a Molecularly Doped Polymer Over Wide Dynamic Ranges

摘要

Transient conductivity measurements have been carried out in a hydrazone-polycarbonate molecularly doped polymer over wide dynamic ranges of time and current as a function of the applied electric field.These data are plotted using both linear-linear and log-log axes.The plots on linear-linear axes give familiar results:an initial spike followed by a relatively flat current before the transit time;a mobility that equals published values and precisely follows the Poole-Frenkel law,being exponential in the square root of the electric field;and a current after the transit time that falls much more slowly than can be accounted for using Gaussian statistics.The same data plotted using log-log axes reveals the behavior over long times and low currents.Before the transit time,the decrease of the current can be characterized by two power laws,but it only decreases by about a factor of 2 from 10~(-2)of the transit time to the transit time and is almost independent of electric field from 5 to 80 V/mu m.After the transit time the current decreases algebraically as t~(-1.75)to a current value of about 10~(-2)of the value at the transit time and is also almost independent of electric field.Available theoretical models are not consistent with these data.We note a surprising coincidence:the current transients are virtually identical to the current transients obtained in molecular crystals,as if disorder does not play a role in determining the shape of the current transients in molecularly doped polymers.