The “formal quantum yield” of the sensitization of the anodic photocurrent of zinc oxide by Rhodamine B has been determined by means of an electrochemical cell technique. Zinc oxide was used as a single crystal in the electrochemical cell +normalIndium|normalZnO crystal|normalElectrolyte+normalDye|normalPlatinum− in aqueous and methanol electrolytes. Simultaneously, the adsorption of the dye on zinc oxide powder has been measured. The influence of the solvent on the extent of the adsorption is significant. The important role of the cosensitizer on the sensitizing ability of the dye is discussed.

By means of two experimental techniques, the sensitization of the conductivity and the discharge both of ZnO single crystals and zinc oxide-resin layers with rhodamin B, eosin, and methylene blue have been studied. Stimulated by current-voltage and capacitance measurements with ZnO single crystals in a suitable electrochemical cell, the sensitization was investigated of anodically polarized ZnO crystals by dyes soluted in the electrolyte of the electrochemical cell: + In || ZnO single crystal || electrolyte + dye || platinum -. A strong increase of the anodic current was obtained by illumination with the corresponding light through the crystal from the backside. In addition to the photovoltage, the photocurrent of the anodically polarized ZnO was measured as a function of the dye concentration in the electrolyte at a constant voltage (2 V). To get more information on the mechanism, these experiments were completed by discharge measurements both of ZnO-resin layers and ZnO single crystals charged under a corona with a dc voltage. The dyed zinc oxide was illuminated under similar conditions. At approximately the same surface concentration of the corresponding dye (as mentioned for the electrochemical experiments) and at the same flux of photons, the decay of the surface potential both of ZnO single crystal and a ZnO-resin layer with the time was measured under illumination with light of various wavelengths. Some experiments on the influence of a second dye in the electrolyte on the extent of sensitization by the first dye are discussed.

By means of two experimental techniques, the sensitization of the conductivity and the discharge both of ZnO single crystals and zinc oxide-resin layers with rhodamin B, eosin, and methylene blue have been studied. Stimulated by current-voltage and capacitance measurements with ZnO single crystals in a suitable electrochemical cell, the sensitization was investigated of anodically polarized ZnO crystals by dyes soluted in the electrolyte of the electrochemical cell: + In || ZnO single crystal || electrolyte + dye || platinum -. A strong increase of the anodic current was obtained by illumination with the corresponding light through the crystal from the backside. In addition to the photovoltage, the photocurrent of the anodically polarized ZnO was measured as a function of the dye concentration in the electrolyte at a constant voltage (2 V). To get more information on the mechanism, these experiments were completed by discharge measurements both of ZnO-resin layers and ZnO single crystals charged under a corona with a dc voltage. The dyed zinc oxide was illuminated under similar conditions. At approximately the same surface concentration of the corresponding dye (as mentioned for the electrochemical experiments) and at the same flux of photons, the decay of the surface potential both of ZnO single crystal and a ZnO-resin layer with the time was measured under illumination with light of various wavelengths. Some experiments on the influence of a second dye in the electrolyte on the extent of sensitization by the first dye are discussed.

No abstract

Geeignete Farbstoffe, wie z. B. Rhodamin B, Erythrosin und Bromphenolblau, haben sich als gute Sensibilisatoren für den gehemmten Ladungsdurchtritt durch die Phasengrenze ZnO/Elektrolyt bewahrt, wobei die ZnO‐Elektrode als Anode operiert. Es wurde nun gefunden. daß Brom‐ und Jodionen die sensibilisierende Wirkung des Rhodamin B deutlich erhöhen. Diese Erscheinung hängt mit der Fluoreszenzlöschung dieser Ionen zusammen. Ferner wurde beobachtet, daß mit steigender Viskosität die Sensibilisierung des Photostroms kleiner wird, was mit einem Rückgang der Fluoreszenzlöschung im Zusammenhang steht. Durch eine geeignete Anordnung konnte ferner nach‐gewiesen werden, daß das während der Belichtung entstehende Jod mit Rhodamin B reagiert und die anfänglich hohe cosensibilisierende Wirkung schwächt.