Carrier Transport in Selenium-Based Amorphous Multilayer Structures

Abstract

Time-of-flight experiments have been employed to determine the drift mobility of charge carriers in various selenium-based amorphous multilayer photoreceptors. The data illustrate the validity of the interpretations of the transient current signals. The addition of As to amorphous selenium progressively decreases both hole and electron drift mobility in the photogeneration layer of these photoreceptors. The results are interpreted in terms of As-induced shallow traps. In recent years, there has been a lot of interest in amorphous Se-based multilayer photoreceptors for xerography and laser printing [1–4]. In these devices the photogeneration of charge and subsequent transport of carriers is separated functionally, that is, these processes occur in different layers. Multilayer structures are very advantageous because the composition of different layers can be tailored independently to meet specific requirements such as spectral sensitivity, good charge transport properties, stabilisation and resistance against environmental interactions. A typical double-layer photoreceptor structure consists of a relatively thin (a few micrometres) Se-based layer for carrier generation, referred to as the photogeneration layer (PGL), and a thick ( ≈ 50 μm) pure selenium layer, referred to as the charge transport layer (CTL). There are also triple-layer photoreceptors, consisting of a transport layer, photogeneration layer and a third thin layer whose function is to protect the PGL layer and improve the charge acceptance of the photoreceptor.