Pulse reverse electrodeposited NiCo2S4 nanostructures as efficient counter electrodes for dye-sensitized solar cells

Abstract

Dendritic nanostructures of NiCo₂S₄ were deposited onto a transparent conducting glass substrate by a facile one step electrodeposition method and were used as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The NiCo₂S₄ thin films were deposited by both potentiostatic (PS) and pulse reverse (PR) electrodeposition techniques and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Both PS and PR techniques produced dendrite-like NiCo₂S₄ nanostructures. CV and EIS measurements revealed excellent electrocatalytic activities for the I⁻/I₃⁻ redox reaction for DSSCs. Sequential CV scanning further showed the high electrochemical stability of the NiCo₂S₄ dendritic nanostructures. The CEs prepared by the PR and PS techniques displayed power conversion efficiency of 7.03% and 6.01%, respectively, which are better than in the control device with thermally deposited Pt. Due to the large surface area of the NiCo₂S₄ dendrite structures and high electrocatalytic activity towards the reduction of I₃⁻ to I⁻, the electrodes demonstrated high solar cell conversion efficiency. This simple and low cost electrodeposition technique shows promise for large scale production of environmentally friendly and highly efficient NiCo₂S₄ CEs for DSSC applications.