The effect of pre-thermal treatment of TiO₂ nano-particles on the performances of dye-sensitized solar cells

We have demonstrated the effect of pre-thermal treatment of TiO₂ nano-particles on the performances of dye-sensitized solar cells (DSCs) by using high specific surface area and anatase only TiO₂ nano-particles (ca. 340 m²/g, Sachtleben Chemie GmgH, represented as HK). TiO ₂ particles and thin films were characterized with X-ray diffraction, FT-IR, UV-Vis diffuse reflectance spectroscopy and FE-SEM. The photoelectrochemical properties of the thin films and the performances of DSCs were measured by photocurrent densities, AC impedance spectra and photocurrent-voltage curves. Before coating the raw TiO₂ of HK (HK-raw) on transparent conducting oxide (TCO) glass for DSC fabrication, pre-thermal treatment of HK-raw by calcining at 450 °C (HK-450) was an essential step to achieve the optimum properties in terms of morphological feature, crystallinity, specific surface area and photocurrent density. HK-450 film showed the high adsorption of dye, high photocurrent density and low interface resistance between TiO₂ and TCO glass, R_TiO2/TCO and TiO₂ and redox electrolyte, R_CT, resulting in the superior photovoltaic performance on the DSC fabricated with HK-450 and Eosin Y (or ruthenium 535 bis-TBA) at AM 1.5: open-circuit voltage of 0.62 V (0.77 V), short-circuit current of 3.03 mA/cm² (22.80 mA/cm²), fill factor of 0.57 (0.44) and overall conversion efficiency of 1.06%, (7.52%). Accordingly, the optimization between the morphological feature, specific surface area and photocurrent density of TiO₂ substrate is promising to accomplish the improved overall conversion efficiency of DSC.