Arival-time detection in drift mobility experiments: Applications to anthracene and azulene

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Abstract
The time‐of‐flight technique for studying charge transport in a slab or film of photoconductive insulator is modified by using an interdigital electrode to monitor both the average current density in the sample and the rate at which charges arrive at its surface. The latter is a sensitive and graphic indicator of what charges are doing in the sample. The theory of the device and several tests and illustrative applications are presented. Among the applications are (a) observation, in anthracene, of electrons and holes separately when both contribute to the total photocurrent and (b) determination of a mobility for holes in azulene, a case in which the results of conventional time‐of‐flight experiments are inconclusive. Appendices contain a general discussion of induced charges and currents and present a variational principle for solving a mixed boundary‐condition problem in electrostatics.