Printed single-walled carbon-nanotubes-based counter electrodes for dye-sensitized solar cells with copper-based redox mediators

Here we report printed single-walled carbon nanotubes (SWCNT) as a promising catalyst material for copper redox shuttles based electrolyte in dye-sensitized solar cells (DSSC). The SWCNT layers, which were printed at low temperature could serve as an alternative catalyst material since they outperformed the traditional thermally platinized CEs by exhibiting very low charge transfer resistance (similar to 2.1-2.9 Omega cm(2)) in both complete DSSCs as well as in a symmetrical CE-CE cells. The superior catalytic activity of printed SWCNT-CEs contributed to better photovoltaic performance and resulted in a higher solar-to-electrical conversion efficiency (7.0% +/- 0.4%) than traditional Pt-CE based DSSCs (6.2% +/- 0.4%) in full sunlight conditions. The devices fabricated with printed SWCNTs catalyst counter electrodes also exhibited impressive open circuit voltage that almost approached 1 Volt. The champion DSSC with SWCNT CE gave a 7.5% conversion efficiency under full sun illumination and 8.3% under half sun illumination. These two efficiency values are the highest ever-reported efficiencies for SWCNT-based CEs combined with a Cu-based electrolyte in DSSCs. These results could provide a pathway for efficient DSSC-based devices, which can be integrated in futuristic consumer applications for efficiently working under both full sun light and low light intensities.