The dye-sensitized nanocrystalline TiO 2 film solar cells were fabricated here. The TiO 2 electrodes were prepared by a sol-gel process and were sensitized by the nature dye extracted from a paper mulberry tree. When the sintering temperature of TiO 2 films rises from 90 to 500 °C, the energy conversion efficiency of the solar cell improves considerably and up to an optimum value at 470 °C. To investigate this, the nano-TiO 2 films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-Vis spectrum, and the current-voltage (I-V) characteristic of the heteroj unction between the nano-TiO 2 and the indium tin oxide (ITO) was measured. The results show the size, crystal phase and band gap of TiO 2 nanoparticles undergo changes at the various sintering temperatures. Besides, the resistance of the heteroj unction decreases with increasing the sintering temperature. As the temperature going up and beyond 450 °C, the heterojunction begins to develop into a Schottky junction, and its potential barrier decreases.
