Hole transport mechanism of the HP-Indigo organic photoconductor (OPC), is measured using the time-of-flight (TOF) technique. Transport is analyzed and found to be Gaussian throughout the whole temperature range, indicating the absence of deep traps in this material. Hole mobilities and diffusion coefficients are obtained as separate parameters for the various external fields and temperatures measured, and functional dependencies on these parameters are determined. Diffusion coefficients are found to grow with the electric field at much greater rates than mobilities, so that Einstein relation is violated. A relation between diffusivity and mobility is proposed for this MDP which displays dispersive Gaussian transport. The transient photocurrents are calculated by a one-dimensional Brownian motion model with reflecting and absorbing boundaries which fit the experimental results.The dependencies of mobilities and diffusion coefficients on temperature and electric field are further used to numerically calculate xerographic discharge curves (V-light decay) which show good fitting to those measured on HP-Indigo's machines. This work can be further extended to several directions in order to describe processes affecting printing. Examples are: lateral conductivity, dot gain (2D), dark decay, and residual effects (V-light degradation) which can be studied by simulating cyclic repeating process of charging and discharging the OPC.
Nurith Schupper, Rafael Kahatabi, Reut Diamant, Doron Avramov, "Modeling Hole Transport Mechanism in an Organic Photoconductor" in Proc. IS&T Int'l Conf. on Digital Printing Technologies and Digital Fabrication (NIP27), 2011, pp 156 - 159, https://doi.org/10.2352/ISSN.2169-4451.2011.27.1.art00040_1