TiO2-CuO three-dimensional heterostructure obtained using short time photochemical deposition of copper oxide inside a porous nanocrystalline TiO2 layer

Abstract Solid inorganic three-dimensional nanocrystalline heterostructures are being studied lately, particularly, regarding photovoltaic structures and as a possible alternative to a solid dye sensitized solar cell (DSSC). Unbiased electron injection from copper species to porous nanocrystalline TiO 2 has been reported recently for TiO 2 –copper oxide photoelectrodes immersed in an aqueous electrolyte; demonstrating that relative position of band edges of these two nanocrystalline semiconductor oxides under illumination encourages pursuing a three-dimensional nanocrystalline TiO 2 –Cu x O heterostructure. Here, copper oxide deposition inside a porous nanocrystalline TiO 2 film using a more efficient photochemical deposition technique is studied further and described. Samples obtained using UV-radiation incident through the conducting glass substrate and samples radiated from the TiO 2 side are prepared and studied. Relative concentration of copper species in the TiO 2 surface layer is analyzed using Rutherford backscattering spectrometry (RBS). Comparison of both sample types gives an idea of copper species distribution along the incident direction of the reaction-provoking UV-radiation. XPS analysis of TiO 2 surface was used to determine oxidation state of copper species present, as well as, their relative proportions. AFM images and roughness analysis clearly show the effect of the dependence of UV-radiation absorption with penetration distance. Finally, the photocurrent dependence with time corresponding to both sample types is studied, compared and explained.