Charge Dynamics Study of the Percolation Threshold in a Polymer-Fullerene Composite System

A fullerene percolation threshold has been identified in the current density-voltage (J-V) characteristics of a 5-(2’-ethyl-hexyloxy)-p-phenylene-vinylene (MEH-PPV) conjugated polymer and fullerene (C60) composite system. Charge dynamics associated with the percolation threshold was studied in this work by means of time-of-flight (TOF) measurements of the charge carrier mobilities. The hole mobility showed little change up to a fullerene concentration of 1 wt.%. On the other hand, the electron mobility increased with increasing fullerene concentration and exhibited a critical behavior with a maximum at a percolation threshold of 0.8 wt.%, at which a minimum in the energetic disorder took place.