Mesh-shaped nanopatterning of Pt counter electrodes for dye-sensitized solar cells with enhanced light harvesting

A facile process to produce large-area platinum (Pt) counter electrode platforms with well-arrayed, mesh-shaped nanopatterns using commercially available TiO₂ paste and poly(dimethyl siloxane) (PDMS) nanostamps is presented. The process involves mesh-shaped (200 nm x 200 nm) nanopatterning of a TiO₂ scaffold onto a fluorine-doped tin oxide (FTO) substrate, followed by Pt sputtering. The structure and morphology of the counter electrodes are characterized by a field emission scanning electron microscope (FE-SEM) and an atomic force microscope (AFM). Solid-state dye-sensitized solar cells (ssDSSCs) fabricated with these mesh-shaped Pt counter electrodes showed an efficiency of 7.0%. This is one of the highest efficiencies observed for N719 dye and is much higher than that of devices with non-patterned, thermally deposited electrodes (5.4%) or non-patterned, sputtering deposited electrodes (5.7%). This improvement is attributed to enhanced light harvesting and a greater surface area and has been confirmed by incident photon-to current efficiency (IPCE), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) measurements.