Analysis of hysteresis and transport regimes using the normalized differential conductance in hybrid inorganic/organic nanocomposites

摘要

Hysteresis in the current-voltage characteristics is usually observed in several types of materials and devices. Its origin is still controversial and the subject of intense research even to date. The interest in this phenomenon is constantly renewed as new materials that exhibit this characteristic are developed because of its undesired effects on the performance of different devices like solar cells and sensors. The space charge limited current spectroscopy is a technique frequently used to study transport in general and it has been used particularly to identify the dominant mechanisms during different branches of the current voltage hysteresis loops. The transport regimes are identified from the slope of double logarithmic plots of the experimental data. This methodology is relatively poor, particularly when linear regions of those plots are narrow or even non-existent. Thus, more efficient and detailed analytical techniques are required. One of these techniques is based on the use of the normalized differential conductance. This function allows obtaining hidden information of the transport mechanism not available with the traditional methodology. The use of this method to study the hysteresis is analyzed in this work. Different nanocomposites, made of chitosan or polyvinyl alcohol, containing gold nanoparticles or carbon nanotubes as fillers, whose current-voltage characteristics exhibit hysteresis when subjected to applied voltage cycling, are used as a test workbench for the proposed methodology. Whereas different normalized differential conductance versus voltage curves are obtained for forward ramps, the same behaviors during reverse ramps are observed for all the materials, indicating clearly a change of the transport mechanisms. From the voltage dependencies, it is possible to conclude that whereas bulk mechanisms dominate during forward ramps, interface or electrode mechanisms are more important during reverse ramps. Published under license by AIP Publishing.