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Cobalt sulfide counter electrodes for the dye-sensitized solar cell (DSSC) were successfully prepared on fluorine-doped tin oxide (FTO) glass substrates by a facial one-step in situ solvothermal method. The influences of prepared temperature on the synthesized phase, surface morphology, electrocatalytic, and photovoltaic performances of the cobalt sulfide counter electrodes were investigated with X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Tafel, and photocurrent density-voltage ( J- V) measurements. The results indicated that very thin CoS nanoparticle thin films grew on the FTO substrates and the CoS counter electrode prepared at 180 °C showed superior electrocatalytic activity, chemical stability, and photovoltaic performance. The DSSC based on the CoS counter electrode prepared at 180 °C exhibited an efficiency of 6.59 % which was comparable to the solar cell based on the sputtering Pt counter electrode (6.82 %). It indicated that CoS in situ growing on FTO glass substrate at 180 °C is a potential candidate to replace Pt as a low-cost and efficient counter electrode of DSSC. [ABSTRACT FROM AUTHOR]

Hexagonal single crystal CoS1.097 nanoplates with the size of 200~500 nm have successfully in situ grown on flexible graphite paper (GP) and FTO substrates with a one-step hydrothermal method, which are used as counter electrodes (CEs) of dye-sensitized solar cells (DSSCs) and show different microstructures and different electrocatalytic activities for I3− reduction. The DSSC based on CoS1.097/GP CE shows larger fill factor and higher short-circuit current density than the DSSCs with Pt/FTO CE and CoS1.097/FTO CE, which attribute to the excellent electrical conductivity of GP and predominant electrocatalytic activity of hexagonal single crystal CoS1.097 nanoplates with the addition of a small electrocatalytic contribution of GP. Therefore, the DSSC with the CoS1.097/GP CE shows the highest photoelectric conversion efficiency (6.99%) among these DSSCs. Furthermore, the CoS1.097/GP CE still shows excellent electrochemical and mechanical stability in the iodine-based electrolyte after enduring the S-type mechanical perturbation. This work indicates the flexible CoS1.097/GP electrode is a promising candidate to replace Pt/FTO CE as a Pt-free, FTO-free, low cost, exceptionally stable, and high-efficient CE of DSSC. [ABSTRACT FROM AUTHOR]