One-step electrochemical deposition of Ni1−xMoxS ternary sulfides as an efficient counter electrode for dye-sensitized solar cells

Abstract

Ternary sulfides of Ni_1−xMo_xS films with various compositions (x = 0, 0.05, 0.1, and 0.2) were fabricated on a fluorine doped tin oxide (FTO) glass substrate by a simple one-step electrochemical deposition method. The electrochemically deposited ternary sulfides were utilized as a low-cost and highly efficient platinum free counter electrode (CE) for dye-sensitized solar cells (DSSCs). The structure, surface morphology and elemental composition of the electrochemically deposited ternary sulfides were examined by using X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM) and energy dispersive X-ray spectroscopy (EDS). A phthaloylchitosan (PhCh) based polymer electrolyte was used as an electrolyte for DSSCs. Cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization studies revealed that the Ni_0.95Mo_0.05S CE exhibited lower charge-transfer resistance at the CE/electrolyte interface and higher electrocatalytic activity towards the regeneration of I⁻ from I₃⁻ relative to other compositions. The Ni_0.95Mo_0.05S ternary sulfide offers a positive synergistic effect for the electrochemical catalytic activity towards the reduction of I₃⁻, which may be due to an increase in active catalytic sites and low-charge transfer resistance and achieved a high power conversion efficiency of 7.15% with a V_oc of 0.65 V, a J_sc of 17.21 mA cm⁻², and a FF of 0.64 with a PhCh-based polymer electrolyte, which is comparable to that of the conventional Pt CE (7.20%). The present investigation demonstrates that the electrochemically deposited Ni_0.95Mo_0.05S ternary sulfide is a promising candidate as a low-cost and highly efficient CE in DSSCs.