Facet-dependent NiS2 polyhedrons on counter electrodes for dye-sensitized solar cells.

Octahedral and cubic NiS2 nanocrystals enclosed by {111} and {100} planes were separately used as counter electrodes (CEs) incorporated into Pt-free dye-sensitized solar cells (DSSCs). The DSSC assembled by NiS2 octahedrons exhibited a conversion efficiency of 5.98%, better than that by NiS2 cubes (5.43%). DFT calculations indicate that the better catalytic effect could be ascribed to higher surface energy, more active sites, and more suitable adsorption energy of {111} planes compared with the {100} planes.