Self-supported construction of nanorod-based hierarchical NiCo2S4 as high-performance electrode for solar cells

Low catalytic capacity caused by the insufficient contact between an electrolyte and a counter electrode material is still a bottleneck for the commercial use of dye-sensitized solar cells (DSSCs). This is because the microstructure is uncontrollable during the preparation of such materials, which are prone to accumulation and collapse, resulting in a low electron transfer rate and high charge transfer resistance. Herein, the self-supported construction of hierarchical nanorod flower (RF) and hierarchical nanosphere flower (SF) consisting of ultrathin NiCo₂S₄ nanosheets was designed for their application as counter electrode catalysts, wherein the entire preparation process was controllable and efficient. Transmission electron microscopy and scanning electronic microscopy results indicated that the RF structure has a better three-dimensional spatial structure. Moreover, the power conversion efficiency of the RF structure was higher than those of the SF structure and noble Pt. This is mainly because the RF structure has a larger contact area than the SF structure. Therefore, with the RF structure, electrons are more likely to shuttle inside the material, thereby increasing the activity of the electrode material and improving its catalytic capacity and conductivity. This study will make an important contribution to the research of DSSCs in which the counter electrode is Pt-free.