In order to obtain highly efficient tandem dye-sensitized solar cells (tandem-DSSCs), the preparation of high-quality p-DSSCs and n-DSSCs respectively are crucial. n-DSSCs have developed rapidly, while this article focuses on p-DSSCs based on NiO electrodes. NiO films were obtained by primary hydrothermal method (pri-NiO) and improved hydrothermal method (imp-NiO) based on different reaction solution concentration, respectively. SEM results show that the morphology of NiO changes from flocks consisting of nanosheets to flower-like microspheres and gridding. Imp-NiO has controllable thickness, more uniform surface and higher specific surface area than pri-NiO. As a result, the efficiency of DSSCs based on imp-NiO is twice as high as that of pri-NiO. (c) 2013 Elsevier B.V. All rights reserved.