Performance and stability of TiO2/dye solar cells assembled with flexible electrodes and a polymer electrolyte

Solid-state, flexible TiO2/dye solar cells were assembled using flexible electrodes, a polymer electrolyte with I−/I3− and a Pt coated counter-electrode. The efficiency of the cells was enhanced when the plastic electrodes coated with TiO2 were exposed to UV radiation, followed by heating at 140 °C in dry conditions. For comparison, a similar cell was prepared by the same procedure but using glass electrodes. The performance of these cells was investigated during a period of 50 days by current–potential and electrochemical impedance spectroscopy measurements. The flexible, solid-state TiO2/dye solar cells (1 cm2) presented an open circuit potential of 0.72 V, short-circuit current of 60 μA cm−2 and an efficiency of 0.32% under a light intensity of 10 mW cm−2. This efficiency was maintained until the fourth day after assembling and decayed to 0.17% on the 14th day, remaining constant until the 40th day and decreasing to 0.13% on the 50th day. Impedance spectroscopy revealed that the series resistance increased with time, lowering the cell efficiency. This effect was not so evident for cells assembled with glass electrodes. Therefore, the flexible electrode limits the preparation of the porous TiO2 photoelectrode and creates a large series resistance in the solar cell. However, these results are very promising for developing solar cells with lower costs and broader applicabilities.