A CuO/TiO 2 interface with potential use for solar light conversion is studied. Thin films are synthesized using a mixture of commercially available nanocrystalline TiO 2 and CuO powders. Samples with mass concentrations from 5 to 10% of CuO in TiO 2 were prepared from a colloidal suspension using a 'doctor blade' technique. Heat treatment (500 °C, 1 h) was used to generate crystals necking and improve adhesion to substrates. X-ray diffraction analysis and scanning electron microscopy indicate that the CuO nanocrystals are smaller than those of TiO 2 . Since TiO 2 does not absorb light in the spectral range where the CuO absorption edge is located, it was possible to obtain an effective CuO absorption coefficient spectra and then extract the bandgap energy. The results confirm the potential use of CuO as a TiO 2 inorganic sensitizer for solar light. SEM images show a mesoporous structure for all samples that would facilitate penetration of a hole conductor and guarantee a large three-dimensional interface. Photocurrent direction with no bias confirms electron transfer from the CuO to the TiO 2 when CuO/TiO 2 films are used as photoelectrodes. Therefore, excited electrons in the CuO conduction band occupy levels with energy greater than the empty states in the TiO 2 conduction band. Possible technological improvements to increase electron collection are discussed.
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