In situ fabrication of Co0.85Se and Ni0.85Se hierarchical thin films as high-performance counter electrode for dye-sensitized solar cells.

Cobalt selenide (Co 0.85 Se) and nickel selenide (Ni 0.85 Se) hierarchical thin films assembled using by nanosheets and nanoparticles, respectively, were fabricated in situ on fluorine-doped tin oxide substrates in a ligand-free environment to prepare counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) consisting of a N719-sensitized nanocrystalline TiO 2 film. The Co 0.85 Se- and Ni 0 . 85 Se-based CEs were rapidly synthesized via a microwave-assisted one-step method at 170 °C within a short reaction time of 10 min. The morphology and structure of the Co 0.85 Se and Ni 0.85 Se hierarchical thin films were characterized by means of scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results of electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel polarization measurements showed that both CEs exhibited good electrocatalytic activity and I − /I 3 − redox reactions and much lower charge-transfer resistance. A power conversion efficiency (PCE) of 8.58% for the Co 0.85 Se CE-based solar cell was obtained, which is comparable to that of cells using Pt CEs (8.57%); 7.09% PCE was obtained for the Ni 0.85 Se-based CE. The results suggest that in situ-prepared Co 0.85 Se-based CEs could be a promising alternative to Pt-based CEs for DSSCs. [ABSTRACT FROM AUTHOR]