The dye-sensitized solar cells based on the interconnected ternary cobalt diindium sulfide nanosheet array counter electrode

Highlights: • The ternary CoIn₂S₄ CE was fabricated by in situ solvothermal synthesis. • The CoIn₂S₄ CE displays an interconnected nanosheet array structure. • The solvent and In_2.77S₄ intermediate play key roles on the formation of CoIn₂S₄. • DSSC based on the CoIn₂S₄ CE gives an efficiency of 8.83%. - Abstract: The ternary cobalt diindium sulfide (CoIn₂S₄) counter electrode (CE) with interconnected nanosheet array structure is fabricated on the fluorine-doped tin oxide (FTO) substrate by in situ ethanol solvothermal synthesis. The ethanol solvent and In_2.77S₄ intermediate play important roles on the formation of the interconnected nanosheet array structure. The dye-sensitized solar cell (DSSC) with the optimized ternary CoIn₂S₄ CE gives an energy conversion efficiency of 8.83%, which is much higher than that of DSSCs based on the binary CoS₂ (6.47%), and In_2.77S₄ (0.46%) CEs and can be comparable with that of Pt CE (8.19%) under full sunlight illumination (100 mW cm⁻², AM 1.5 G). Except for the intrinsically electrocatalytic activity from the CoIn₂S₄, the higher conversion efficiency of CoIn₂S₄ based DSSC can be attributed to that the interconnected nanosheet array structure provides plentiful catalytic active sites, abundant electron transport channels, and fast electrolyte diffusion.