Charge transport through a polymer foil

The charge-transport mechanism in FEP (A) polymer foils charged with an ethyl alcohol contact has been studied by measuring the decay of voltage across the foils. Each foil was metallized on one surface and stored at 100 °C in an open-circuit configuration. Voltage decay is shown to occur by charge transport through the foil and to be in good agreement with the predictions of a model in which charge is transported by hopping of injected carriers between localized trapping centers. The model is characterized by three parameters: the free-carrier mobility, the mean free time of a carrier between traps, and the mean capture time in a trap. Evaluation of these parameters enables the effective carrier mobility at long decay times to be estimated—e.g., with a charging voltage of −500 V, the effective mobility of negative charge carriers in FEP (A) approaches 2.2×10−16 cm2/V sec at 100 °C.