2.3. Fabrication and Characterization of DSSC Based on TiO2 Nanoflowers

The fabrication of a DSSC based on TiO₂ nanoflowers was done as reported elsewhere [22]. For the photoanode, a slurry of the synthesized TiO₂ nanoflower powder (0.2 g) was made by mixing it with aqueous polyethylene glycol (PEG, 4 wt.%) solution. An incremental addition of PEG solution was important to achieve a uniform TiO₂ slurry. The prepared TiO₂ slurry was spread by the doctor blade method over the framed fluorine-doped tin oxide (FTO) glass substrates and kept for 10 min to dry. Afterward, the TiO₂-coated FTO substrate was calcined at 450 °C for 30 min. Consequently, the TiO₂-coated FTO substrate was kept for dye absorption by immersing it into 0.3 mM ethanolic solution of N719 dye at room temperature for 16 h in the dark. After dye absorption of the required time, ethanol solvent was used to rinse the dye-absorbed TiO₂-coated FTO substrate and removed non-absorbed dye from the TiO₂ surface, and finally dried in an oven under nitrogen stream at 40 °C. To prepare the counter-electrode, a thin layer (~80 nm) of platinum (Pt) was coated with the ion sputtering technique on the cleaned FTO glass substrate. The DSSC assembly was made by combining the counter (Pt-coated FTO) and photoanode (dye-absorbed TiO₂-coated FTO) and sealed with a separating Surlyn sealing sheet (60 μm) using a hot plate. The redox electrolyte, made of 0.05 mM I₂, 0.2 M tert-butyl pyridine in acetonitrile, and 0.5 M LiI, was inserted through one of two small holes initially made on the counter electrode. The fabricated DSSC possessed an active area of 0.25 cm².