Properties of the Cr/Pt bilayered film employed dye sensitized solar cells with low temperature annealing

The properties of the Cr/Pt bilayered catalytic layer with additional low temperature annealing using a dye sensitized solar cell (DSSC) were investigated. A DSSC device with a structure with an effective area of 0.45 cm² glass/FTO/blocking layer/TiO₂/N719 (dye)/electrolyte/50 nm Pt/50 nm Cr/glass was prepared. For comparison, 100 nm-thick Pt and Cr counter electrodes on flat glass substrates were also prepared using the same procedure. The sheet resistance was examined using a four point probe. The photovoltaic properties, such as the short circuit current density, open circuit voltage, fill factor, energy conversion efficiency (ECE), and impedance, were characterized using a solar simulator and potentiostat. The phases of the bilayered films were examined by X-ray diffraction. The microstructure of the bilayered films was characterized by atomic force microscopy. The measured sheet resistance of the counter electrode with annealing increased to. The measured ECE of the dye-sensitized solar cell devices with vacuum annealed Cr/Pt bilayer counter electrodes decreased abruptly. The interface resistance at the interface between the counter electrode and electrolyte increased as the annealing time increased. The increase in catalytic activity of the Cr/Pt bilayer before annealing resulted from the effect of a compressive strain field. After 10 minutes, the strain field was removed by annealing. The new phases of Pt₃Cr and CrPt by annealing led to drastically decreased catalytic activity.