Properties of an Au/Pt bilayered counter electrode in dye sensitized solar cells

A 0.45 cm² dye-sensitized solar cell (DSSC) device with glass/FTO/blocking layer/TiO₂/dye/electrolyte/50 nm Pt/50 nm Au/glass was prepared to improve the energy conversion efficiency by applying an Au/Pt bilayer to the flat glass substrate of the counter electrode (CE). For comparison, Au and Pt CEs, 100 nm in thickness, on flat glass substrates were also prepared using the same method. The photovoltaic properties, such as the short circuit current density (J_sc), open circuit voltage (V_oc), fill factor (FF) and energy conversion efficiency (ECE), were checked using a solar simulator and potentiostat. The strain of a Pt thin film was examined by x-ray diffraction. The sheet resistance and interface resistance were examined using a four point probe and impedance measurements. The measured energy conversion efficiencies of the dye-sensitized solar cell devices with Pt only and Au/Pt bilayer counter electrodes were 4.60% and 5.28%, respectively. The Au/Pt bilayer was confirmed by XRD, which also revealed a large compressive strain of −6.66 × 10⁻³ in the Pt layer. The interface resistance at the interface between the counter electrode and electrolyte decreased when an Au/Pt bilayered thin film was applied. The increase in efficiency at the Au/Pt bilayered counter electrode was attributed to the effect of a compressive strain field formed at the Pt layer and the low resistive Au layer used.