ELECTRICAL-CONDUCTIVITY IN IODINE-DOPED ETHYL CELLULOSE

The electrical conductivity of solution-grown ethyl cellulose (EC) fil ms, 5-30 mum thick, has been studied in the sandwich configuration (me tal-EC-metal) as a function of iodine concentration from 0.5 to 5.0 wt % ratio. The studies were conducted in the temperature range 333-383 K , while the field was varied over the range (3.0-5.5) x 10(4) V/cm. Al uminium was used as the lower electrode, while the upper electrode was of Al, Ag, Cu, Au or Sn. Certain transient effects such as a large bu rst of current immediately after the application of field were observe d. An attempt was made to identify the nature of the current by compar ing the observed dependence on electric field, electrode material and temperature with the respective characteristic features of the existin g theories of electrical conduction. The results show that the electri cal conduction follows Ohm's law at lower fields, while at higher fiel ds, space-charge limited current (SCLC) was observed. It was also foun d that Richardson-Schottky emission was responsible, to some extent, f or the transport of charge carriers in the polymer. The conductivity o f the films increased on doping with iodine. The dopant molecules are considered to act as additional trapping centres and provide links bet ween the polymer molecules in the amorphous region, thus resulting in the formation of charge transfer complexes.