Design for a-Si H Photoreceptor

The photoreceptor of electrophotography is a charge depletion device in which replenishing carriers from the electrodes must be completely prohibited. Since the a-Si H is a typical ambipolar material in which both carriers, i.e., electrons and holes, are allowed to move, great care must be paid to the contact with either the conductive electrode or the free surface 

The metal-insulator—semiconductor (MIS) structure is employed in the heterophase blocking where the thickness of the insulator used is the key factor in satisfying the blocking requirement. Differently from the solar cell with MIS structure, in which an insulating film tens of angstroms thick is used to avoid the back-diffusion of photoinduced carriers (Wronski et al., 1981), the photoreceptor of electrophotography has necessarily a rather thick insulating film to block carrier transport. 

We can find various types of photoreceptors in the patent literature (Tabei et al., 1980 Nakagawa et al., 1981) dealing with a-Si H and organic materials however, details are lacking. 

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