Fabrication of Sheet sphere ZnO nanostrutures by wet chemical method and using them in dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs), have received considerable attention due to low cost and easy fabrication process. The photoanode is composed of a wide-bandgap semiconductor that is photosensitized by an organic dye . The dye molecules absorb sunlight in the visible range and thereby the electrons excite from the HOMO (highest occupied molecular orbital) level to the LUMO (lowest unoccupied molecular orbital) level. The excited electrons inject to the conduction band of the semiconductor and move through the semiconductor to the back contact. Zinc Oxide nano structures are one of the most widely used materials in the fabrication and synthesis of solar cells. The feature of these nano structures are highly dependent on the conditions of synthesis and fabrication process. In this paper, we have produced two ZnO structures, microsphere and nanosheets-microsphere structures, by changing the pH of the growth solution by wet chemical method. We have shown that the existance of the nanosheets in second structure leads to considerable increase in dye-loading and thereby, increment in light harvesting and efficiency of dye-sensitized solar cells.