Nickel sulfide films with significantly enhanced electrochemical performance induced by self-assembly of 4-aminothiophenol and their application in dye-sensitized solar cells

Abstract

Dye-sensitized solar cells (DSSC) are a promising solution to global energy and environmental problems because of they are clean, low-cost, have high efficiency, good durability, and easy fabrication. However, seeking a platinum (Pt)-free CE alternative with high electrocatalytic activity and low cost to enhance the efficiency of the DSSC still is a key issue. In this study, a novel composite film of 4-aminothiophenol/nickel sulfide (4-ATP/NiS) was prepared by a two-step chemical/electrochemical process and served as the CE for a DSSC. The surface morphology of the 4-ATP/NiS composite film was characterized by field emission scanning electron microscopy (FESEM) and showed a microporous structure. The electrochemical performance of the 4-ATP/NiS (here marked as NiS*) counter electrode (CE) was evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel curves, which revealed that the NiS* CE possessed excellent electrocatalytic activity for the reduction reaction of triiodide to iodide and low charge transfer resistance at the interface between the electrolyte and CE, respectively. The DSSC assembled with the novel NiS* CE achieved an enhanced power conversion efficiency of 7.20% under the irradiation of 100 mW cm⁻² as compared to that of the DSSC based on a Pt electrode. Thus, this concept and therefore a significant enhancement in power conversion efficiency can be applied to other DSSCs with Pt-free CEs such as polyaniline, poly (3,4-ethylenedioxythiophene), graphene and so on.