Electron transport in doped and undoped polymers containing π-conjugated groups

Abstract

Electric conduction behaviors were studied as for several polymers as a function of dopant concentration and the pyrolysis temperature. A weak electronic conduction is found to exist even in undoped states of poly(p-phenylene sulfide), poly(m-phenyleneisophthalamide) and poly(ethylene 2, 6-naphthalate). The electronic conductivities of undoped poly(p-phenylene) and polythiophene are presumed to be very low. Stable semiconducting films were obtained from poly(p-phenylene sulfide) doped with organic acceptors. The principal effect of introduction of the organic dopants is enhancement of the carrier mobility. A close relationship between the conductivity and the activation energy for conduction process is found in the doped poly(p-phenylene sulfide) family. From this relation, it is concluded that the conduction mechanism is based on the hopping one and metal-insulator transition does not occur in that doped with AsF5. Light pyrolysis of polyimide was a useful procedure for obtaining tough semiconducting films. Enhancement of the conductivity by pyrolysis is attributed to the development of the conjugated double bonds and closely connected with increase of the carrier mobility. © 1985 The Society of Polymer Science, Japan. All Rights Reserved.