Experiments on Dye Sensitization of Zinc Oxide

Abstract

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.

Efficiency Enhancement of Dye-Sensitized Solar Cells’ Performance with ZnO Nanorods Grown by Low-Temperature Hydrothermal Reaction

“…During the process, an amount of Zn 2+ ions are dissolved into the solution from the surface of the ZnO nanorods. Subsequently, aggregation of Zn 2+ ions with sensitizer dyes occurs, and the phenomenon was reported for several organic sensitizer dyes as well as ruthenium complexes [ 25 , 26 ]. Once aggregation takes place in DSSCs, the power conversion efficiency will dramatically decrease [ 27 ].…”

On the Influence of Sensitization of the Electron Transfer Through the Interface Zinc Oxide/Electrolyte by Salt Additions

“…According to Eq. [12a] and [12b] and taking [lla] and [llb], respectively, into consideration, the cosensitized current/cos can be stated as /cos : ks'[DQ] [15] Substituting and rearranging Eq. [13], [14], and [15] Icos…”

“…Then they were exposed to light of a defined photon flux and wavelength in a closed chamber with a revolving plate and a translucent probe for potential measurements. The exact experimental details have been published (15).…”

Effects of Electronic Excitation on Reaction Rates at the Solid‐Electrolyte Interface

“…11band 11c. Such cases have been found for excited dye molecules adsorbed on the surface of suitable semiconductors, especially ZnO [30,31,32], CdS [33], GaP [34], Sn02 [35], AgCl, AgBr [36]. One recognizes that this scheme represents a mechanism for spectral sensitisation of semiconducting materials, a process which has been extensively used and studied in connection with the problem of photographic image formation.…”