Effects of the morphology of nanostructured ZnO films on the efficiency of dye-sensitized solar cells

The main aim of this work was to examine the physical characteristics of nanostructured thin films used in dye-sensitized solar cells. Parameters such as the thickness and the morphology of the films were investigated, as these factors greatly affect the efficiency and the stability of dye-sensitized solar cells. To this aim, nanostructured ZnO films of varying thickness (from 2 to 17 pm) were prepared and sensitized with simple organic dyes, such as the dye molecules Bengal Rose and Rhodamine B. It was observed that the efficiency of the cells depends strongly on the thickness of the ZnO films and that an optimum film thickness exists that yields the highest efficiency results, for each type of sensitizer considered in the study. In addition, the presence of aggregates of ZnO nanoparticles that are formed on the surface of the films was examined. These aggregates affect the morphology of the films, whose surface becomes coarse and irregular and also affect the performance of the resulting dye-sensitized solar cells. (C) 2011 Elsevier Ltd. All rights reserved.