High‐Performance Cobalt Selenide and Nickel Selenide Nanocomposite Counter Electrode for Both Iodide/Triiodide and Cobalt(II/III) Redox Couples in Dye‐Sensitized Solar Cells

The nanocomposites of cobalt selenide and nickel selenide (Co 0.85 Se/Ni 0.85 Se) were successfully fabricated on FTO glass by a facile co‐electrodeposition method at ambient temperature. Nanocomposite films were used as electrocatalysts in dye‐sensitized solar cell counter electrodes for regeneration of both iodide/triiodide and cobalt(II/III) redox couples. Co 0.85 Se/Ni 0.85 Se were mainly composed of nanoflakes and nanoparticles. It is noted that such nanostructure generated by nanoparticles embedded with 2D nanoflakes led to high active sites and was accessible to cobalt(II/III) electrolyte, delivering better catalytic activity for the reduction of larger volume cobalt(II/III). As a result, for cobalt(II/III) electrolyte, the Co 0.85 Se/Ni 0.85 Se based dye‐sensitized solar cell performed significantly improved efficiency than that of Pt and Co 0.85 Se. Meanwhile, the Co 0.85 Se/Ni 0.85 Se based dye‐sensitized solar cell held comparable energy conversion efficiency to that of Pt and Co 0.85 Se for iodide/triiodide electrolyte.