A spectroscopic study was carried out on charge generation processes in a multilayered photoreceptor comprising a specific bisazo compound as charge generation material. Photoreceptors comprising a charge generation layer (CGL), composed of a bisazo compound dispersed in a binder resin, and a charge transport layer (CTL) incorporating an electron donor molecule in a binder resin, were treated as model photoreceptors for experimental and numerical analysis. Charge generation model, which had been previously described for a single layer organic photoconductor with charge generation predominately occurring at layer surface, was expanded and applied in a numerical study to a conventional dual layer system. A change in spectral response was observed as a result of variation in CGL thickness for both conventional dual layer and inverted dual layer (CTL overcoated with CGL) systems. These experimental results were compared with numerical simulations in the expanded charge generation model. Analytical results suggested that charge generation sites existed at CGL-CTL interface and that estimated energy diffusion length was much longer than exciton diffusion length reported for organic materials. Moreover, the author's proposed charge generation model showed superior agreement with experimental results compared to conventional bulk generation model.
S. Yokota, "Spectroscopic Study on Charge Generation in Bisazo-Based Layered Photoreceptor" in Journal of Imaging Science and Technology, 2010, pp 40505-1 - 40505-6, https://doi.org/10.2352/J.ImagingSci.Technol.2010.54.4.040505