Highly transparent NiCo2S4 thin film as an effective catalyst toward triiodide reduction in dye-sensitized solar cells

In this study, a transparent NiCo2S4 thin film as an effective counter electrode (CE) was incorporated into a Pt-free dye-sensitized solar cell (DSC) for the first time. NiCo2S4 was synthesized via a facile solvothermal method and then subjected to electrophoresis onto a fluorinated tin oxide (FTO) glass substrate. X-ray diffraction, energy dispersive spectrum, and field-emission scanning electron microscope confirmed that the NiCo2S4 nanoparticles were successfully synthesized and deposited onto the FTO substrate, while the electrochemical analyses showed its superior electrocatalytic activity for the I3− reduction compared to the conventional Pt CE. Additionally, the NiCo2S4 CE demonstrated a high transmittance (> 75%) at visible wavelengths. Thus, the DSC assembled with the transparent NiCo2S4 CE achieved a promising photovoltaic conversion efficiency of 6.14% in comparison with that using the Pt CE (6.29%).