Effect of Temperature on the Stability of Nickel Sulphide Reduced Graphene Oxide Nanocomposite Counter Electrode in Quantum Dot-Sensitized Solar Cells

Abstract Quantum-dot sensitized solar cells (QDSSCs) are equipped with counter electrodes (CEs) based on reduced graphene oxide (rGO) and nickel sulphide (NiS/rGO). A hydrothermal method at 150°C with variable reaction times (5h, 10h, and 15h), was used to synthesize NiS/rGO CEs and evaluate their electrocatalytic activity, stability, and mechanical adhesion under varying conditions at (25°C, 40°C, 60°C, 80°C) for 100h. Electrochemical performance was assessed through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization. Results showed that NiS/rGO 5h exhibited superior electrocatalytic activity, achieving a significantly higher current density. CV results showed that NiS/rGO 5h generated the highest current density of 112.4 mA/cm 2 at 80°C (Pt = 8.07 mA/cm 2), and lower charge-transfer resistance (R ct values, 3.567 Ω·cm 2 at 80°C than (Pt = 674.4 Ω·cm 2). The high performance was attributed to the dominance of β-NiS phase. Additionally, the nanocomposites demonstrated strong mechanical adhesion and stability under prolonged exposure to elevated temperatures. This study highlights the potential of NiS/rGO nanocomposites as cost-effective and efficient alternatives to Pt for improved QDSSC performance.