A study of the photoelectrochemical properties of KTaO₃ and ZnO in alkaline electrolytes

In this work, single crystals of n-type, semiconducting oxide photoelectrochemical cell photoanodes have been investigated. The central focus of this study was the growth and characterization of n-type Potassium Tantalate (KTaO₃) single crystals as a function of doping elements and doping concentration. The purpose of these investigations was to exploring the use of semiconducting oxides in PEC cells for solar energy applications. The doped tantalate crystals were examined using a variety of electrical, optical, and photoelectrochemical techniques that included: current-voltage, capacitance-voltage, quantum yield, optical transmission, and ellipsometry. Quantum yield measurements were performed in the PEC cell configuration both as a function of illumination wavelength and time. Zinc oxide (ZnO) was also studied in detail as a PEC Cell photoanode material since it is known to have a higher photo-response and a direct band edge, in contrast to KTaO₃. The oxides Barium Tantalate (BaTiO₃) and Strontium Tantalate (SrTiO₃) were also examined. Although, doping did not affect the wavelength of the onset of optical absorption in any of the samples, it did affect some of the electrical characteristics as well as the measured photo-response during PEC cell operation.