Achievement of 4.7% conversion efficiency in ZnO dye-sensitized solar cells fabricated by spray deposition using hydrothermally synthesized nanoparticles.

ZnO-based dye-sensitized solar cells (DSSCs) have been fabricated using hydrothermally synthesized ZnO nanoparticles by spray deposition. The effect of self-assembled nanostructures in ZnO photoelectrodes, due to the electric field during spray deposition, has been studied. Thickness of the photoelectrode is found to play a role on the cell performance, the cell with nanocrystalline film thickness of ∼4.3 µm yielding an efficiency of ∼2.8% for a cell area of ∼3.2 cm(2). On the other hand, the cell with ZnO nanostructures is found to yield an efficiency of 4.7% (enhancement of ∼60%) which is highest for the cell with area>1 cm(2) having a photoelectrode thickness of ∼4.5 µm. Increased surface area due to the presence of ZnO nanostructures in the photoelectrode film helps in the adsorption of more dye molecules to the ZnO surface, which contributes to the better cell performance. The improved dye-sensitized solar cell performance is also explained with the help of light scattering by the ZnO nanostructures through extending the distance traveled by light so as to increase the light-harvesting efficiency of the photoelectrode film.