One-step solvothermal tailoring the compositions and phases of nickel cobalt sulfides on conducting oxide substrates as counter electrodes for efficient dye-sensitized solar cells.

Several nickel cobalt sulfide (Ni-Co-S) counter electrodes (CEs) are prepared, and the Ni-Co-S nanoparticles are in-situ grown on SnO 2 : F (FTO) transparent conductive glasses via a facile solvothermal process, in which thiourea is used as the sulfurizing reagent. The X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometer are employed to measure the microstructure and composition of the Ni-Co-S CEs. When a proper amount of thiourea is adopted, fine crystalline NiCo 2 S 4 CE is obtained. When the amount of thiourea is small or large, (Ni,Co) 4 S 3 or (Ni,Co) 3 S 4 CE is acquired, respectively. Cyclic voltammetry, electrochemical impedance spectroscopy, Tafel polarization and open-circuit voltage decay (OCVD) measurements all demonstrate that the electrocatalytic activities and electrical conductivities of these Ni-Co-S CEs all approach or exceed those of Pt-pyrolysis CE. Their superior electrochemical performances are further confirmed by fabricating DSSCs with the Ni-Co-S CEs, they display similar or better photo-electric conversion efficiencies to/than the Pt-pyrolysis counterpart. [ABSTRACT FROM AUTHOR]