Morphological control of platinum nanostructures for highly efficient dye-sensitized solar cells

Cyclic electro-deposition (CED) is a cost-effective tool to synthesize nanostructures with a solution process, controllable morphology and high purity. Here we report novel platinum nanostructures fabricated according to CED at room temperature in solution containing H₂PtCl₆ precursor and NaNO₃. Remarkable Pt nanostructures - from nanoclusters, nanosheets, nanograsses to nanoflowers - were produced through morphological control via variation of either period of CED scans or concentration of the precursor. Pt films with uniform nanograss structures have great electro-catalytic performance (electron-transfer resistance = 0.3 Ω) and intrinsic light-scattering (reflectivity ∼50%), perfectly suitable for use as counter-electrodes for dye-sensitized solar cells (DSSCs). The DSSC device made with the Pt-nanograss counter-electrode and N719 dye attained efficiency η = 9.61% of power conversion, which is 12% enhanced from that fabricated according to a conventional thermal decomposition method (η = 8.55%) under similar experimental conditions. When the devices were further optimized with a thick TiO₂ film (17 + 5 μm) sensitized by Z907 dye using the CED-Pt counter-electrode, we obtained J_SC (mA cm^-2) = 19.44, V_OC (V) = 0.742, and FF = 0.736, giving an exceptional power conversion efficiency of 10.62%.