The electrophotographic process on the films of polyvinylidene fluoride (PVF₂) was realized and investigated. It is shown, that the illumination of the polarized film leads due to the pyroelectric effect to the formation of the surface charge, which may be developed by the cascade method. The contribution of the photoconductivity and the bulk photovoltaic effect is analized.

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Electrophotographic properties of some benzo (thia) pyrylium salts having a trimethine group as a sensitizer for brominated PVK have been studied. These sensitizers were synthesized by the reaction of a 2-methyl benzo (thia) pyrylium salt with ethyl orthoformate.
Thus we found that these sensitizers have spectral response in near infra-red region and show high sensitizing ability. The replacement of oxygen to sulfur atom in a benzopyrylium ring results in the shift of the spectral response to longer wavelength region but the enhancement of the sensitizing ability is not observed. (Sensitization, Sensitizer, Benzo (thia) pyrylium Salt, Trimethine Group, Brominated PVK)

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The effects of crude or finished β-CuPc and chemical property of binder resin to electrophotographic properties of photoreceptor have been studied. Electrophotographic properties of the photoreceptor depend on particle size and shape of β-CuPc and interaction between β-CuPc and binder resins.
Electrophotographic sensitivity of crude type β-CuPc (needle type) resin layer is higher than that of finished type β-CuPc resin layer.
The electrophotographic characteristics of finished type β-CuPc resin layer especially depend on chemical properties of binder resins. Novolak type resin having phenyl radical and/or hydroxyl group have little effect to the free carrier generation in the photoreceptor, while acrylic type resin having ester and/or carboxyl group is very effective to the free carrier generation. The use of finished type β-CuPc is effective to selection of binder resins of the photoreceptor, The measurements of the contact potential difference and the photovoltage also give effective information to selection of binder resins and CuPc photoconductor.
The photoreceptor of needle type β-CuPc and acrylic resin has good electrophotographic properties and the sensitivity is 4.13 lux sec under the exposure of white light.

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ZnO powders have been prepared chemically from zinc-sulfate, chloride, nitrate and acetatevia zinc oxalate and their photoconductive properties have been studied comparing with those of a commercial ZnO powder for photoreceptor use prepared by a physical process, i. e., oxidation of vapor of zinc. Effects of metal doping and firing temperature of the zinc oxalate on the photoconductivity of the ZnO powders have also been studied. The dark and photo-conductivity of the ZnO powders were measured using a surface type electrode without binder. All the measurements were made by the dc method in an evacuated chamber.
All the undoped ZnO powders showed photosensitivity to UV light, but the photosensitivities depended on the starting materials. The photosensitivity of the commercial ZnO powder is higher than those of the undoped ZnO powders prepared in this study. Doping of metals such as Cr, Na and Pb did not extend the photoconductive spectra to the longer wavelength region but increased the photosensitivity.
The activation energy for the dark conduction is 1.7 eV for the commercial ZnO, indicating the intrinsic conduction, while those are in the range of 0.36 to 0.52 eV for undoped ZnO in this study, indicating the extrinsic conduction. According to the TSC measurements, it has been confirmed that the ZnO powders with deeper traps are less photosensitive.
The most eminent difference in the photoconductive behavior between the chemically prepared ZnO and the commercial one is the rise and decay characteristics of the photocurrents. The photoresponse of the former is fast, while those of the later are very slow.

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