Increased efficiency of ZnO dye-sensitized solar cell using hierarchical nanowires

Abstract

The novel selective hierarchical growth approach represent low cost, all solution hydrothermal process that yields complex hierarchical ZnO nanowire photoanodes by utilizing a simple manipulation of seed particles and capping polymer was demonstrated to increase the total power conversion efficiency. As the result of the hierarchical nanowire structure, the overall light-conversion efficiency was nearly five times than the efficiency of simple vertically aligned ZnO nanostructure DSSCs. The increase of efficiency is correspond to significantly enhanced photo-anode surface area for higher dye loading, light harvesting and decreased the charge combination by direct conduction path along the “nanotree” structure. As the length of the branches increased, the branches became flaccid and the increase in solar cell efficiency slowed down because the effective surface area increase was hindered by branch bundling during the drying process and subsequent decrease in the dye loading.