A novel Pt-free counter electrode for dye-sensitized solar cells: Nickel sulfide hollow spheres

•Nickel sulfide hollow spheres have been prepared by a one-step hydrothermal method with no template.•A hollow structure provides a higher electrolyte absorption, which could be used as counter electrode in dye-sensitized solar cells.•The DSSC consisted of hollow NiS CE showed a PCE of 6.9% which is comparable to that of Pt CE (6.75%).

NiS has a high conductivity and excellent catalytic properties. Furthermore, a hollow structure provides a higher electrolyte absorption, which could be used as counter electrode in dye-sensitized solar cells. In this paper, NiS hollow spheres have been prepared by a traditional one-step hydrothermal method. The dye-sensitized solar cell with NiS hollow spheres as a counter electrode yielded a preferable power conversion efficiency of 6.90%, which was comparable to that of platinum (6.75%) as counter electrode.