Fabrication of dye-sensitized solar cells with TiO2 photoelectrode prepared by sol-gel technique with low annealing temperature

Transparent titanium oxide (TiO2) photoelectrodes for dye-sensitized solar cells (DSCs) were deposited on fluorine doped tin oxide substrate by a sol-gel dip coating technique with acetic acid as an acid catalyst, where crystallinity can be achieved at a relatively low annealing temperature. Repetitive dip coating and drying, with two intermediate annealing, has made this technique easier to prepare TiO2 thin film with desired thickness within a short period of time. The TiO2 photoelectrodes were annealed at various temperatures to study the effect of annealing temperature on the photovoltaic property of the DSCs. The structure of the TiO2 films, prepared at various annealing temperatures, shows different crystallinities. Good crystallinity has been observed for 300 degrees C annealing temperature and it improved with increasing annealing temperature. The surface morphology, investigated by field emission scanning electron microscope and atomic force microscope measurements, revealed that with the increase in annealing temperature, the surface of TiO2 photoelectrode showed more porous structure with higher roughness. The DSCs with TiO2 photoelectrode, annealed at 300 degrees C, showed the best photovoltaic characteristics among the three samples of investigation. Measurement of optical properties and incident photon-to-current conversion efficiency indicated the maximum dye incorporation in TiO2 electrode, deposited at 300 degrees C. The solar cell efficiency and fill factor of this above mentioned sample are 0.96% and 46.3%, respectively. The results indicate a strong correlation between the microstructure, dye absorption, and photovoltaic property of the sample.