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). TiO2 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, RTiO2/TCO and TiO2 and redox electrolyte, RCT, 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.