TiO₂ Crystallization at Room Temperature and Preparation of Transparent Carbon Counter Electrode for Low-Cost Dye-Sensitized Solar Cells

We developed a low-cost dye-sensitized solar cell (DSSC) using TiO₂ fabricated via rapid breakdown anodization (RBA) and ultrafast room-temperature crystallization (URTC). The prepared TiO₂ was deposited on a self-made fluorine-doped tin oxide (FTO) conductive glass, and the FTO/TiO₂ system was sensitized using curcumin dye. The DSSC was constructed by sandwiching the FTO/TiO₂/curcumin electrode with an I⁻/I₂ electrolyte and a transparent carbon counter electrode prepared using a liquid–liquid interface system. The characterization results showed that the TiO₂ freshly prepared via URTC was transformed into an anatase crystalline phase, which exhibited a 3.10 eV band gap and a 10.08 nm average crystallite size, comparable to those of the TiO₂ prepared via the conventional 450 °C annealing treatment (3.13 eV, 11.60 nm). The photocurrent activity of the URTC-prepared TiO₂ under ultraviolet light (0.10 mA/cm²) was also comparable to that of the annealed TiO₂ (0.12 mA/cm²). In addition, a transparent carbon electrode (FTO/C_t) was prepared successfully; it exhibited a ±58.26% transparency under visible light and comparable electrocatalytic activity to Pt-coated FTO. The DSSC based on FTO/TiO₂-URTC/curcumin and FTO/C_t showed front and back illumination efficiencies of 0.47% and 0.26%, respectively. These results are only slightly lower than those of the conventional DSSC with FTO/annealed TiO₂/curcumin//FTO/Pt, which exhibited front and back illumination efficiencies of 0.52% and 0.36%, respectively.