An Interconnected Ternary MIn S (M=Fe, Co, Ni) Thiospinel Nanosheet Array: A Type of Efficient Platinum-Free Counter Electrode for Dye-Sensitized Solar Cells.

The ternary iron-group thiospinels of metal diindium sulfides (MIn S , M=Fe, Co, Ni) with a vertically aligned nanosheet array structure are fabricated through an in situ solvothermal method on F-doped tin oxide (FTO) substrates, which are employed as one type of platinum (Pt)-free counter electrodes (CEs) in structure-dependent dye-sensitized solar cells (DSSCs). A DSSC assembled with ternary CoIn S CE achieves an photoelectric conversion efficiency (PCE) of 8.83 %, outperforming than that of FeIn S (7.18 %) and NiIn S (8.27 %) CEs under full sunlight illumination (100 mW cm , AM 1.5 G), which is also comparable with that of the Pt CE (8.19 %). Putting aside that the interconnected nanosheet array provides fast electron transfer and electrolyte diffusion channels, the highest PCE of CoIn S based DSSC results from its largest specific surface area (144.07 m  g ), providing abundant active sites and the largest electron injection efficiency from CE to electrolyte.