An Interconnected Ternary MIn₂S₄ (M=Fe, Co, Ni) Thiospinel Nanosheet Array: A Type of Efficient Platinum‐Free Counter Electrode for Dye‐Sensitized Solar Cells

Abstract

Abstract The ternary iron‐group thiospinels of metal diindium sulfides (MIn 2 S 4 , 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 2 S 4 CE achieves an photoelectric conversion efficiency (PCE) of 8.83 %, outperforming than that of FeIn 2 S 4 (7.18 %) and NiIn 2 S 4 (8.27 %) CEs under full sunlight illumination (100 mW cm −2 , 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 2 S 4 based DSSC results from its largest specific surface area (144.07 m 2 g −1 ), providing abundant active sites and the largest electron injection efficiency from CE to electrolyte.