The relevant physical processes in the photodischarge of a homogeneous photoreceptor

The relevant physical processes involved in the photodischarge of an electrophotographic plate consisting of a homogeneous photoconducting layer are reviewed in light of recent investigations. Typical examples of this type of photoreceptor are amorphous Se and poly-N-vinylcarbazol complexed with trinitro-fluorenone. The essential behavior of this type of photoreceptor can now be quantitatively described in terms of the basic properties of the photoconductor. This description views the photodischarge process as consisting of the photoinjection of free carriers and their transport across the layer. The photoinjection process is determined by the photogeneration of free carriers and their recombination. The transport of the free carriers is characterized by their drift mobility and trapping. To be suitable for the electrophotographic application it is essential that the density of deep traps whose trapping times are long compared to the process time be low. In such materials it is seen that the photoinjection efficiency determines the sensitivity of the layer in the electrophotographic process.