Effect of N719 Dye Adsorption Into Composition of Different Sized TiO2 Films for Photovoltaic Performance of the Dye-Sensitized Solar Cells

Effect of N719-dye adsorption into TiO2 films prepared via incorporating small (similar to 15 nm) and large (similar to 300 nm) TiO2 nanoparticles at several ratios were investigated to improve the photovoltaic efficiency of dye-sensitized solar cell. The photovoltaic efficiency is significantly improved after incorporation of large and small TiO2 nanoparticles. From experimental result, the composition with 70% small: 30% large TiO2 is found as an optimum mixing ratio for the best performance (5.57%) of a dye-sensitized solar cell. This high photovoltaic performance is attributed to an effect of following factors. Besides an increase in dye molecules adsorption, the light scattering of over layer large TiO2 enhances harvesting light of the solar cells and the under layer small TiO2 ensures good electronic contact between film electrode and the fluorine-doped tin oxide glass substrate. However, we found that the composition with 50% small: 50% large TiO2 was adsorbed much more N719-dye molecule than that of the other mixtures of TiO2 and hence resulting in a decrease photovoltaic performance. This decrement of performance may be attributed to the decreased surface area and dye aggregation.