Urchin-inspired ZnO-TiO 2 core-shell as building blocks for dye sensitized solar cells

Abstract We applied the core-shell concept to an urchin-inspired ZnO nanowire photoanode building block as a means to increase the electron transport and reduce recombination between nanowire and electrolyte. Dye-sensitized solar cells (DSSCs) were prepared, for the first time, from arrays of urchin-like ZnO nanowire building blocks covered with a thin layer of anatase TiO 2 by atomic layer deposition (ALD). An increase in the cell open-circuit voltage ( V OC ) and an improvement in the conversion efficiency were observed when the urchin-like ZnO building blocks were coated with 10 nm thick TiO 2 ALD shells in combination with 10 μm thick top layer of TiO 2 nanoparticles of 15.8 nm size. Using urchin-like ZnO nanowires as building blocks can improve the light-scattering and provide a higher surface area with a great control of the nanowire dimensions to increase the dye loading and reduce the electron collection path. The addition of a thin TiO 2 blocking layer decreases the recombination of charges in such a high surface area nanostructure.