Time stability of dye-sensitized solar cells based on ZnO sphere aggregates sensitized by N719 was systematically investigated. Eight cells in two groups were involved in this study. Each group has four cells that were connected in series and were used to supply the power to a light emission diode. Group 1 was kept in a room and Group 2 was kept outside ambient condition. The duration was half a year. The cells of the two groups can maintain about 90% of their initial efficiency after half a year running. The decrease of efficiency mainly results from about 15% drop of current density in the first week. Then the current density remained unvaried in the following days no matter whether the cells were kept in the room or outside ambient condition. The open-circuit voltages of these cells increased from 0.67-0.72 to 0.71-0.76 V in the first week and then kept unvaried in the following operation. These results indicate an excellent time stability of DSCs based on aggregates of ZnO spheres sensitized by N719 and suggest a great potential for practice use. (C) 2011 Elsevier B.V. All rights reserved.