Charge carrier generation and charge carrier separation in organic photoreceptors are reviewed with attention to the dissociation processes of excitons into free carriers. Special emphasis has been placed on the striking differences in the mechanism of the charge carrier formation process between organic and inorganic semiconductors. Two dominant mechanisms of exciton dissociation caused by an electrostatic field are reviewed : (a) due to the Schottky-barrier, and (b) due to the local field caused by ionically-adsorbed oxygen molecules. The former is discussed on the basis of a merocyanine solar cell and the latter through the thermal photocurrent-quenching effect observed in β-copper phthalocyanine. The above dissociation processes occur, more or less, at the same time in all organic photoreceptors. Hence, photoreceptors should be designed by taking into consideration which mechanism prevails.

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The purification technique and the effects of purification on the dark and photoconductivities of vacuum evaporated phthalocyanine thin film are reported. Metal-free and copper phthalocyanine were purified by a simple train sublimation technique. Variation of the impurity contents with the purification was investigated by a mass analysis. The impurities in phthalocyanine pigments have been mostly removed by the purification.
The dark and photoconductivities are decreased due to the removal of impurities by the purification. The decrease of photoconductivity is due to the density of exciplex and the probability of dissociation of excitons in the the local electric field near the impurities.

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This paper describes the results of experimental determination of the electron affinities of polystyrene (PS), poly (2-vinylpyridine) (PVP), poly (2-vinylnaphthalene) (P2VN) and poly (N-vinylcarbazole) (PVCz).
We have used two types of electron scattering techniques, electron transmission and electron energy loss experiments with low-energy electron beams, in order to determine the absolute location of the bottom of the conduction bands (the negative of the electron affinity). By comparing the energy positions of the spectral features observed in the two types of spectra, we have determined the electron affinities of PS, PVP, P2VN and PVCz to be 0.4 eV, 0.3 eV, 0.6 eV and 1.8 eV, respectively.
Further, a brief discussion is also made on the method to determine the electron affinity from the low-energy electron scattering by solids.

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The effects of ambient gas on the electrical conductive properties of gallium phthalocyanine (GaClPc) thin films were investigated. The kinds of ambient gas were humid air (humidity 72%), quasi-dry air, nitrogen and oxygen in 10^-5, 10^-2, 50, 100 and 760 Torr. From these results, the I_d-/I_d+ ratio in above 50 Torr showed about 1000 times with remarkable rectification characteristics and there are no non-linear in less than 10^-2 Torr.
Humidity is little effective for this conductivity. Since the GaClPc is electron-donortype, the oxygen of the electron-acceptor type iseasily adsorbed by GaClPc. These result indicate that the oxygen varies from physical adsorption into the chemical adsorption. Oxygen adsorption resulted in an appreciable change in the surfacecharge density. Also, the adsorbed oxygen causes the remarkable rectification characteristic by the strong Schottky effect at the interface.

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A new preparative method for amorphous silicon films, "Chemical Deposition" is proposed, in which silane is decomposed oxidatively to afford the precursors of the film with a chemical reaction of fluorine.
This paper describes general features of the method and properties of the films, i. e., dominating factors of the deposition rate, and the effects of both substrate temperature and the flow ratio of the gases on the chemical structures in the films.
The films show high photoconductivity comparable to those prepared by the rf-glow discharge of silane.

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The hydrophobic surface modification of the hydrogenated amorphous silicon carbide (a-SiC : H) films were developed using of CF₄ plasma treatment.
The contact angle of water drop on a-SiC : H films becomes up to 95° after the CF₄ plasma treatment. A hydrophobic inorganic layers containing C-C (or CH₂) and C-Fn (n=1−3) bonds are formed on the surface of the a-SiC : H films.
The contact angle of water drop on CF₄ plasma treated a-SiC : H films are about 20°larger than those of the as deposited films for the repeated cycles of corona charging.
A new a-Si : H photoreceptor with the CF₄ plasma treated a-SiC : H films for the surface
passivation layer were fabricated. There are little change in the photosensitivity though the
surface potential decreases by 20% after the CF₄ plasma treatment.

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