Reactively sputtered nickel nitride as electrocatalytic counter electrode for dye- and quantum dot-sensitized solar cells

Nickel nitride electrodes were prepared by reactive sputtering of nickel under a N-2 atmosphere at room temperature for application in mesoscopic dye- or quantum dot-sensitized solar cells. This facile and reliable method led to the formation of a Ni2N film with a cauliflower-like nanostructure and tetrahedral crystal lattice. The prepared nickel nitride electrodes exhibited an excellent chemical stability toward both iodide and polysulfide redox electrolytes. Compared to conventional Pt electrodes, the nickel nitride electrodes showed an inferior electrocatalytic activity for the iodide redox electrolyte; however, it displayed a considerably superior electrocatalytic activity for the polysulfide redox electrolyte. As a result, compared to dye- sensitized solar cells (DSCs), with a conversion efficiency (eta) = 7.62%, and CdSe-based quantum dot-sensitized solar cells (QDSCs, eta = 2.01%) employing Pt counter electrodes (CEs), the nickel nitride CEs exhibited a lower conversion efficiency (eta = 3.75%) when applied to DSCs, but an enhanced conversion efficiency (eta=2.80%) when applied to CdSe-based QDSCs.