A Quasi-steady-state Analysis for the Electrophotographic Discharge Process

A description of the electrophotographic discharge process is presented for a homogeneous photoconductor characterized by constant free-carrier lifetimes and trapping times. The physical model is described by a set of one-dimensional nonlinear differential equations with appropriate boundary conditions. It is shown that a quasi-steady-state approximation can be derived which is valid for most of the decay process under typical electrophotographic conditions. In this quasi-steady state, the photoconductor layer can be described by an equivalent circuit which consists of a capacitance in parallel with a two-terminal element whose current-voltage characteristic is directly related to the field-dependent photoinjection efficiency. A numerical analysis using large-scale computation of the solutions to the differential equations has been done for a hypothetical but typical material. The results of this computation, which describe the initial transient behavior and the subsequent quasi-steady-state behavior of the photoconductor, are presented. The results of the quasi-steady-state analysis agree with the actual behavior of amorphous Se. It is suggested that measurement of the quasi-steady-state photodischarge process can be used as a convenient technique for obtaining the field-dependent characteristics of the photoinjection process.