For solar energy devices to become affordable to everyone, the need for developing modest techniques should be given priority attention. In our laboratory we have developed very simple methods for preparation of cobalt oxides, CoOOH and Co3O4, and nickel oxides NiO and NiOOH. They were deposited on glass substrates from solutions containing ammine complexes of the respective metal ions. For cobalt oxides, the initial deposition was of brown CoOOH, which was converted into black Co3O4 by annealing it at 590 K in air. The films were characterized by measuring their optical absorbance, transmittance, and reflectance in the spectral range of 300 - 900 nm. The data were used to calculate the spectral variation of their optical constants. Absorption spectra of the films were analyzed to obtain their optical band gaps. Some possible uses of these films are mentioned, and the prospects of this method for deposition of other oxide films are also discussed.
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