In order to improve the visible response in the Electrofax system, dye-sensitization is available and rosebengal is one of the most excellent sensitizers. Rosebengal is not a good photoconductor but it induces a remarkable improvement in the photoresponse On the other hand, malachitegreen does not sensitize zinc oxide though it is a good photoconductor. This paper describes the mechanism of dye-sensitization process in the Electrofax system.
The photocurrents were measured by single excitation and double excitation with ultraviolet and/or visible radiations in rosebengal dye-sensitized zinc oxide and in pinaflavol dye-sensitized zinc oxide. From these results the increase in the photocurrents was estimated to correspond to the ultraviolet or the visible radiation under double excitation. From these experimental data we may say that exciton was produced in dye by absorbing lights, which excited trapped electrons neaf the surface of zinc oxide particles up to the conduction band and then photoconduction was increased. This conclusion supports A. Terenin's proposal on the dye sensitization of photoconduction.
