▎ 摘　　要

2D Layered transition metal dichalcogenides (TMDs) have great attention concerning their unique electrical and optical properties. Counter electrodes (CEs) are crucial to creating low-cost and high power conversion efficiency (PCE) dye-sensitized solar cells (DSSCs); thereby, the development of high-performance CEs utilizing non platinum (Pt) materials is essential. This study reports on new highly electrochemically active 2D/2D cobalt substituted SnS2/rGO (reduced graphene oxide) heterostructure that had been successfully synthesized by a twostep hydrothermal method with different weight percentages (1, 3 and 5 wt. %) of rGO. The fabricated 2D/2D heterostructure acts as a Pt-free counter electrode in a dye-sensitized solar cell. The crystalline structure, morphology, and chemical state were confirmed by X-ray diffraction (XRD), RAMAN, High resolution scanning electron microscopy (HRSEM), High resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). Among all these, Co-SnS2/rGO (5 wt. %) counter electrode delivers the highest power conversion efficiency of 5.54 % with a short circuit current density (JSC) of 11.85 mA cm  2, open circuit voltage (VOC) of 0.77 V and fill factor (FF) of 60.13. High surface area (59.202 & RARR; 69.148 m2/g), facilitating more active sites via increasing rGO content was analyzed through Brunauer-Emmett-Teller (BET) analysis. Lower peak-to-peak separation (Epp) and charge transfer resistance (RCT) are responsible for the observed improvement in the electrolyte and counter electrode interface. Notably, rGO with Co-SnS2 creates a synergetic effect through fast electron transporting capability. Furthermore, the Co-SnS2/rGO (5 wt. %) CE shows excellent electrochemical stability over 100 cycles in an iodine-based electrolyte. The superior electrocatalytic activity and photovoltaic output highlight the promise of Co-SnS2/rGO (5 wt. %) for DSSCs CE. This efficiency is comparable to the expensive Pt CE (6.0 %).