The photocharge imaging process (chargeless electrophotography) is based on the photovoltaic effect of a photoreceptor. The dependence of the photovoltage and photocharged image density of the undyed zinc oxide binder layer under illumination by bandgap light on log exposure was measured, and the curves of both photovoltage and image density were found to show the solarization phenomenon. It is shown that the photovoltage of pure zinc oxide binder layer consists of three components, that is, the Dember voltage ( V_D ), the variation (Δ V_b ) of the surface potential barrier height on zinc oxide and the negative voltage ( _t ) induced by electron trapping, while the components responsible for the photovoltaic latent images are _D and V_t . It was estimated that the corresponding ASA value (photosensitivity) of the photocharge imaging process may be about 10^-2. It was found that the photocharged latent image of dyed zinc oxide binder layer can be formed under illumination by dye-exciting light, and is developable by electrophotographic liquid developer. The sensitometric curve of the photocharged latent images formed by dye sensitization is analogous to that of the latent images by band-gap light.