Phase-Selective Synthesis of Cobalt Sulfide Heterostructure Catalysts as Efficient Counter Electrodes in Dye-Sensitized Solar Cells

Developing a cost-saving, high-efficiency, and simple synthesis of counter electrode (CE) material to replace pricy Pt for dye-sensitized solar cells (DSSCs) has become a research hotspot. Owing to the electronic coupling effects between various components, semiconductor heterostructures can significantly enhance the catalytic performance and endurance of counter electrodes. However, the strategy to controllably synthesize the same element in several phase heterostructures used as the CE in DSSCs is still absent. Here, we fabricate well-defined CoS2/CoS heterostructures and use them as CE catalysts in DSSCs. The as-designed CoS2/CoS heterostructures display high catalytic performance and endurance for the triiodide reduction in DSSCs thanks to the combined and synergistic effects. As a result, a DSSC with CoS2/CoS achieves a high energy conversion with an efficiency of 9.47 % under standard simulated solar radiation, surpassing that of pristine Pt-based CE (9.20 %). Besides, the CoS2/CoS heterostructures possess a quick activity initiation process and extended stability, broadening their potential applications in various areas. Therefore, our proposed synthetic approach could offer new insights for synthesizing functional heterostructure materials with improved catalytic activities in DSSCs.