Interface phenomena in double-layer organic photoreceptors

Single photogeneration layers of a phthalocyanine pigment dispersed in a polyvinyl butyral binder, and double layers consisting of the photogeneration layer coated with hole transport layers of TPTA, DEH and ED molecularly dispersed in polycarbonate were exposed to single-shot light excitation. The charge collected was measured as a function of temperature, electric field, exposure intensity and duration. The resulting mean transport level of TPTA was found to be 0.17 eV, and that of DEH 0.11 eV, below the valence band of the pigment, but that of ED was found to be 0.09 eV above it. The injection efficiencies were independent of held and amounted to 3 x 10(-3) for TPTA and 0.02 for DEH, at room temperature, but that for ED was 0.1 independently of temperature. Models for the injection efficiencies in these cases are also discussed in this work for the first time.