Evaluation of Microwave Plasma Sintering for the Fabrication of Dye Sensitized Solar Cell (DSSC) Electrodes

Dye-sensitized solar cells (DSSCs) have demonstrated considerable potential due to their solar energy conversion efficiency and their fabrication from relatively low cost materials.^1,2 Titanium dioxide (TiO₂) nanoparticles are widely used in the fabrication of the DSSC electrodes.² There is a considerable energy requirement however required for the sintering of the TiO₂ particles during the fabrication of the mesoporous electrodes. This study investigates the use of microwave (MW) plasma treatments as a rapid, energy efficient processing technique for the sintering of the metal oxide particles. A comparison is made with conventional furnace treatments for the sintering of TiO₂ nanoparticles (Degussa P25), deposited onto fluorine doped tin oxide (FTO) coated glass substrates. Subsequent to the TiO₂ sintering, ruthenium based dye (N719) adsorption studies were carried out for coatings heated using both sintering techniques. Based on UV/Vis absorption spectra measurements of 5 mins plasma and 30 mins furnace sintering, it was observed that both sintering techniques exhibited similar levels of dye adsorption. A decrease in the level of dye adsorption was observed for the TiO₂ coatings sintered for longer periods (up to 10 mins in this study). This change with longer plasma treatment times was associated with rutile grain growth and a decrease in surface roughness, possibly due to a densification of the mesoporous structure. The effect of TiO₂ coating plasma treatment times on the conversion efficiency of the dye sensitised electrodes was also evaluated. Plasma treatments of 5 mins were found to yield the highest conversion efficiency of 6.4%.