Effect of molar ratio of zinc nitrate: hexamethylenetetramine on the properties of ZnO thin film nanotubes and nanorods and the performance of dye-sensitized solar cell (DSSC)

Abstract

The effect of hexamethylenetetramine (HMT) concentration while keeping zinc nitrate [Zn(NO3)2] at constant concentration and vice versa on the morphology, optical absorption, structure of ZnO nanostructure and the performance of the DSSC utilizing the ZnO samples has been investigated. The ZnO photoanode samples were deposited on FTO substrate via hydrothermal growth at 90 °C for 8 h followed by cooling at 50 °C for 16 h. It was found that the structure and morphology of ZnO nanostructure are significantly influenced by the molar ratio of precursor concentration. The high density and smaller diameter of ZnO nanorods were formed when molar ratio of OH− ion concentration was increased. The modification on the shape and porosity of ZnO nanostructure are seemingly influenced by the amount of free ion Zn+2 in the growth solution. The samples have been utilized as photoanode in DSSC. The DSSC utilizing ZnO nanosheets performs the J SC, V OC, FF and η of 3.6 mA cm−2, 0.50 V, 0.31 and 0.56 %, respectively. The highest performance of that cell is due to the high density and unique morphology of ZnO nanosheets that offered high specific surface area for higher dye loading and light harvesting.