PERCOLATION-DOMINATED CONDUCTIVITY IN A CONJUGATED-POLYMER-CARBON-NANOTUBE COMPOSITE

We have made electrical measurements on a system using carbon nanotube s as the dopant material. A semiconjugated, organic polymer was mixed with carbon nanotubes to form a wholly organic composite. Composite fo rmation from low to high nanotube concentration increases the conducti vity dramatically by ten orders of magnitude, indicative of percolativ e behavior. Effective mobilities were calculated from the space-charge regions of the current-voltage characteristics for the 0-8 % mass fra ctions. After an initial rise these were seen to fall from 1-8 % dopin g levels as predicted by theory. From the values for conductivity and mobility, an effective carrier density was calculated. This was seen t o decrease between 0% and 1%, before rising steadily. [S0163-1829(98)5 1536-6].