Time-of-flight photocurrent measurements to resolve long-range ordering of transport molecule in a photoreceptor charge transport layer

Abstract

Structure and order within the charge generating, charge transporting, and overcoat layers of an organic photoreceptor can influence the device performance characteristics. Accordingly, the ability to measure the distribution of the active and non-active components within these layers is of fundamental importance. Charge transport dynamics across a semiconducting film of N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine (TPD) doped polycarbonate is investigated via the time-of-flight method. The resulting photocurrent transients indicate a gradient in TPD concentration through the thickness of the film. This conclusion is verified by mapping TPD concentration through the cross-section of the film via Raman microspectroscopy.