Potential-controlled pulse electrochemical deposition of poly nanostructural two-dimensional molybdenum disulfide thin films as a counter electrode for dye-sensitized solar cells

In this study, the poly nanostructure of two-dimensional (2D) layer-nanostructure molybdenum disulfide (MoS2) thin films were synthesized onto the fluorine-doped tin oxide (FTO) glass substrate via the pulse-mode electrochemical deposition (Pulse ECD) method at room temperature and ambient pressure. The surface morphologies of the prepared thin films were examined using field-emission scanning electron microscope (FE-SEM). The chemical states and crystallinities of the prepared thin films were examined by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and high-resolution transmission electron microscopy (HR-TEM), respectively. Cyclic voltammetry (CV) measurements, electrochemical impedance spectroscopy (EIS), and Tafel-polarization measurements were performed to analyze the electrochemical properties and catalytic activities of the thin films for redox reactions. According to the HR-TEM results, it was observed that the poly nanostructural 2D MoS2 owning the short-range-order nanostructure offered the numerous edge planes to provide plenty active sites for an efficient counter electrode (CE) of the dye-sensitized solar cells (DSSCs). In combination with a dye-sensitized TiO2 working electrode and an iodine-based electrolyte, the DSSC assembled with the poly nanostructural 2D MoS2 CE showed a photovoltaic conversion efficiency of 6.08% under the illumination of AM 1.5 (100 mWcm(-2)), which was comparable to that with Pt CE (6.43%). Our study demonstrated that the room-temperature Pulse ECD method displayed a facile and economical process to synthesize the low-cost 2D MoS2 CE for the cost-effective DSSCs.