Cobalt sulfide as counter electrode in p-type dye-sensitized solar cells

We proposed a novel application of cobalt sulfide (CoS) in the configuration of transparent thin film as anode in p-type dye-sensitized solar cell (p-DSC). The anodes here considered have been prepared using a water-based method that is suitable for the large scale production of large-area electrodes. The photoactive cathodes of the p-DSC were mesoporous nickel oxide (NiO) thin films deposited via rapid discharge sintering (RDS). The NiO electrodes were sensitized with the benchmark dye erythrosine B (ERY), while the couple I-/I3- was the redox mediator. The CoS anodes showed higher electrocatalytic efficiency in comparison with the commonly used platinized FTO (Pt-FTO). This was determined by means of electrochemical impedance spectroscopy (EIS) of CoS based dummy cells, with CoS showing a lower charge-transfer resistance with respect to Pt-FTO. The overall conversion efficiency of the p-DSC employing ERY-sensitized NiO as photoactive cathode and CoS anode was 0.026%, a value very close to that obtained with platinized FTO anodes (0.030 %). The external quantum efficiency spectra of the p-DSCs with CoS anodes were similar to those obtained with Pt-FTO anodes under illumination with AM 1.5 solar simulator.