Electrophotographic and charge transport measurements on amorphous semiconductor films of (Se1−xTex)1−yPy

Abstract

Amorphous Se–Te–P photoreceptor films of various compositions were deposited on to Al substrates by conventional vacuum evaporation techniques. Both xerographic and charge transport measurements have been carried out on the films to evaluate their possible suitability for photoreceptor applications. In xerographic measurements, the photoreceptor films were corona charged to a voltage (V0) and then photodischarged by illumination under light of preselected wavelength (λ) and constant intensity (I). Xerographic photosensitivity (S) was obtained from the photoinduced discharge characteristic via the empirical definition S = (V0 – V1/2)/V0t1/2I where V1/2 = V0/2 is half the initial voltage and t1/2 is the time taken to photo-discharge the surface potential to V1/2. The photosensitivity was studied as a function of illumination wavelength and material composition. Charge transport measurements were carried out using a time-of-flight transient photoconductivity technique to determine the electron and hole mobility – lifetime (μτ) products in the films. The results indicate that Se–Te–P alloys have poor xerographic photosensitivity in the short wavelength region (e.g., λ ~ 500 nm) owing to poor electron and hole transport, but in the long wavelength region (e.g., λ ~ 800 nm) the photosensitivity is considerably higher than the Se–Te system.