Designing Metal-Sulfide-Sphere Counter-Electrode Catalysts for ZnO-Nanorod-Array-Based Quantum-Dot-Sensitized Solar Cells

Graphical Highly effective sulfide-sphere counter electrodes are prepared for ZnO nanorod-based quantum-dot-sensitized solar cells. To increase the competitiveness of quantum-dot-sensitized solar cells (QDSCs) among the various photovoltaic devices, it is necessary to develop new counter-electrode (CE) catalysts to replace the unviable Pt CE. Herein, a series of metal-sulfide spheres (e.g., FeS 2 , Co 9 S 8 , NiS, CuS, and ZnS) are designed and synthesized as CE catalysts for QDSCs. As inferred from cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization-curve results, except for ZnS, all of the sulfide spheres perform better than Pt toward S x 2– /S 2– redox-couple regeneration, among which, NiS shows the highest catalytic activity, followed by Co 9 S 8 , CuS, and FeS 2 . The power conversion efficiencies of ZnO nanorod-array photoanode-based QDSCs with sulfide-sphere CEs are 2.5 % (NiS), 2.2 % (Co 9 S 8 ), 1.8 % (CuS), and 0.8 % (FeS 2 ), much higher than that of their Pt CE-based counterparts (0.30 %).