Synthesis of Ellipsoid TiO2 Nanoparticles and Their Application to Photoelectrodes of Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have attracted extensive attention due to their potential low cost and high energy conversion efficiency, rendering them one of the most promising systems for solar-to-energy conversion. At the heart of these solar cells is a mesoporous TiO₂ electrode, which not only provides a high surface area for accommodating the light-absorbing sensitizer but also serves as the stable conductor for photogenerated electrons. Although the solar-to-energy conversion efficiencies were found to be increased resulting from the increased light scattering, such kinds of photoanodes still suffered from low electron transport capability because of their particle stacking nature that forms large quantities of grain boundaries. In this work, we try to synthesis ellipsoid TiO₂nanoparticles which can provide a fast way for electron transport and offer reduced trapping of photoinjected electrons during the path to back contact.

Ellipsoid TiO₂ nanoparticles were synthesized by hydrothermal method. The morphology of the TiO₂ nanoparticle was characterized with a scanning electron microscope. TiO₂ paste was prepared as follows, ellipsoid TiO₂ nanoparticles (1.850g), acetylacetone (0.20ml),  Triton-X (30%, 1.0 ml) and polyethyleneglycol (0.185g) were mixed into acidic water (pH=0.7). The resulting TiO₂ paste was printed by doctor blade method on fluorine-doped SnO₂-coated (FTO) glass electrodes and sintered at 450 °C for 30 min. DSSCs were prepared by a conventional procedure.

According to SEM images of the ellipsoid TiO₂ nanoparticles, particle length and width were 240 and 40 nm, respectively. The ellipsoid TiO₂ powders were characterized by XRD, and determined their crystal structure is anatase. We have successfully fabricated ellipsoid TiO₂ based DSSCs, and their conversion efficiency was 6.8% under AM 1.5 simulated full sunlight (100 mW cm⁻²) illumination.