Hierarchical high-density well-aligned branched ZnO nanostructures are prepared on conductive glass substrates via a facile strategy with an aqueous solution process. The formation mechanism of ZnO array on a ZnO array is discussed based on the coincident lattice between the trunk and branches. Dye-sensitized solar cells (DSSCs) are fabricated using a well-aligned, high-density, and crystalline array of branched ZnO nanostructures (nanorods (NRs), nanotubes (NTs)) as photoanodes. The ZnO trunks provide fast routes for electron transport to the substrate electrode. The branched ZnO nanotubes (B-ZNTs) DSSCs exhibit an overall efficiency of 0.97%, which is a 52% improvement compared with that obtained for ZnO NRs (ZNRs) DSSCs. The better photovoltaic performance of hierarchical ZnO nanoarchitecture DSSCs is due to a higher dye loading and light harvesting as a consequence of the enlargement of the internal surface area and optical scattering from the dendritic structure within the photoanode. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.029207jes] All rights reserved.