INTER-LAYER MIXING EFFECT ON THE TRANSPORT-PROPERTIES OF A DUAL-LAYERORGANIC PHOTORECEPTOR INTERFACE

Dual-layer organic photoreceptors, with applications in electrophotogr aphy, are widely fabricated using solvent-casting techniques. The pres ence of solvent when overcoating the charge generation layer with the charge transport layer suggests that the interface between the two lay ers will not be sharp and may consist of a mixed layer containing both charge transport and charge generation materials. In this work we hav e used transient photoconductivity techniques to examine the effects o n hole transport of adding small amounts (up to a few percent by weigh t) of charge generation material (x-form metal-free phthalocyanine) to a standard charge transport layer (p-diethylaminobenzaldehyde-1,1'-di phenylhydrazone in a polyester binder). The addition of x-form metal-f ree phthalocyanine is found to have no effect on the hole mobility of the transport layers but greatly affects the observed time-of-flight p ulse shapes. It is proposed that the addition of the x-form metal-free phthalocyanine creates deep trapping states and this is supported by simple computer simulations.