Abstract
Spectral sensitization of zinc oxide electrophotographic layers by a series of merocyanine dyes was studied. Although the dyes used in the experiment are much different in adsorption characteristics onto the zinc oxide surface according to the property of the substituent introduced in the dye molecule, all these dyes have the same fundamental structure (5-〔(1-ethyl-4 (H) -quinolylidene-ethylidene〔-rhodanine.) and also have practically the same optical absorption.
From the result of the electrostatic surface potential measurement of the layers it has been shown that the dyes which have polar substituent such as C2H4S03Na or CH2COOH are highly efficient spectral sensitizers.
However, in the case of electrodynamic measurement of the layers by using surface type photoconductive cells, these dyes are found to be almost ineffective as spectral sensitizers. This contradiction may be explained by assuming a shorter range of the mobile elctrons liberated by the photoexcited dye molecules, compared with that of mobile electrons excited by the intrinsic absorption of UV light. This is also confirmed by the fact that the time ef rise and decay of photocurrents observed in the dye sensitized wavelength region is shorter than that of the photocurrents in the intrinsic region.
