It is well known that the dark and photo-decay of coronacharged photoconductor-polymer dispersion layers are given experimentally as the Inoue's equation
V (t) =V
oexp (-a √t),
and Iida found that the plot between log V (t) and t has a linear relation in which the gradient of this linear line is proportional to the square root of the absolute temperature.
There are many explanations and estimations on this coronacharging phenomena. For example, the capacitance and the resistance of the layer change non-linearly with the increase of accumulation of charges in the layer. And, it is also estimated that the surface states of photoconductor change with the temperature and it gives the non-linear effects on the layer's capacitance and resistance. However, it is considered that these assumptions are so complicated that neither the formation of Inoue's equation nor experimental proof will be easily obtained.
So, we considered a model in which corona ions diffuse across the layer along an electrical field after chemisorbing into the layer's surface. Then the differential equations which are derived from the transportation theory of nonequilibrium thermodynamics are calculated. And, the solution of these equations satisfies not only the linearity between log V and, √t but also the linearity of the line gradient against the square root of the absolute temperature. Many experimental results support this solution consistently.
Therefore, we inferred that corona ions diffuse into the layer and this difiusion speed determines the rate of the dark decay of coronacharging processes.
In the case of dark decay process, it seems that the charges of the corona ions, which diffuse to the reverse side of the layer, are neutralized by the positive charges, and they are deposited in the air regions of the grain boundary, or excluded to the outside of the layer. However, in the case of photo-decay process, the electrons-and-holes, which are generated by the light irradiation, neutralize the charges of corona ions at the each surface of photoconductor. It is explained that the corona ions are neutralized rapidly without traveling a long distance. The rate is determined by the diffusion speed along the thickness of around 0. 1, a, then the corona potential decays rapidly in the case of the photo-decay.
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