Fabrication of Solar Cell Devices

TiO₂ paste was prepared by the following method described by Ito et al. in the literature.³⁵ TiO₂ powder was mixed with α-terpineol and ethylcellulose in the ratio of 16.8:4.5:78.7. TiO₂ thin films were prepared by applying the paste on the FTO glass plate using the doctor blade method.³⁶ The TiO₂ electrodes were gradually heated under an air flow at 500 °C for 15 min. The working electrode was composed of a 12–13 μm thick TiO₂ film (active area 0.16 cm²). The dye was absorbed on a TiO₂ film by dipping into 0.5 mM N719 dye solution in ethanol at room temperature for 20 h to complete the loading with a sensitizer. The dye-adsorbed TiO₂ electrode and Pt-deposited glass counter electrode were assembled together into a sealed sandwich-type cell by clips. A drop of electrolyte solution containing 0.6 M 1,2-dimethyl-3-propylimidazolium iodide, 0.05 M I₂, 0.1 M LiI, and 0.5 M tert-butylpyridine in acetonitrile was injected into the assembled cell.