Properties of the nano-thick Al/Pt or Ti/Pt bilayered catalytic layer used in dye sensitized solar cells

Al/Pt and Ti/Pt bilayers to a flat glass substrate were employed as a counter electrode to improve the energy conversion efficiency of a dye-sensitized solar cell device with a structure of glass/FTO/blocking layer/TiO₂/N719(dye)/electrolyte/(50 nmPt-50 nmAl) or (50 nmPt-50 nmTi)/glass. For comparison, a 100 nmthick Pt counter electrode on a flat glass substrate was also prepared using the same method. The sheet resistance was examined by a four point probe. The photovoltaic properties, such as the short circuit current density, open circuit voltage, fill factor, energy conversion efficiency, and impedance, were characterized using a solar simulator and potentiostat. The phases of the bilayered films were identified by X-ray diffraction. The measured energy conversion efficiencies of the dye-sensitized solar cell devices with Al/Pt and Ti/Pt bilayer counter electrodes were 5.36% and 5.03%, respectively. The interface resistance at the interface between the counter electrode and electrolyte decreased when the Al/Pt and Ti/Pt bilayer thin films were applied. The new phases of AlPt₃ and Pt₃Ti led to a decrease in resistivity and an increase in catalytic activity. This suggests that Al/Pt and Ti/Pt bilayer thin films might improve the efficiency of dye-sensitized solar cells.