MoS
2 thin films with marigold flower-like nanostructures were grown on conductive fluorine-doped tin oxide (FTO) substrates through a one-step hydrothermal synthesis for their application as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). Different MoS
2 thin film samples (A–D) were grown on FTO slides using different concentrations of precursors (sodium molybdate and thioacetamide), while keeping the Mo/S molar ratio constant (1:4.6), in all samples. The effect of varying precursor concentrations (3.2–12.6 mM on MoS
2 basis) on the structure of the nanostructured thin films and their performance as DSSC-CEs was investigated. Scanning electron microscopy revealed a material with an infolded petal-like morphology. With increasing precursor concentration, the petal-like structures tended to form bunched nanostructures (100–300 nm) resembling marigold flowers. X-ray diffraction analysis, X-ray photoelectron, and Raman spectroscopy studies showed that the thin films were composed of hexagonal MoS
2 with good crystallinity. Hall effect measurements revealed MoS
2 to be a p-type semiconductor with a carrier mobility of 219.80 cm
2 V
?1 s
?1 at room temperature. The electrochemical properties of the thin films were examined using cyclic voltammetry and electrochemical impedance spectroscopy. The marigold flower-like MoS
2 thin films showed excellent electrocatalytic activity towards the I¯/I
3¯ reaction and low charge transfer resistance (
Rct) values of 14.77 Ω cm
?1, which was close to that of Pt electrode (12.30 Ω cm
?1). The maximum power conversion efficiency obtained with MoS
2 CE-based DSSCs was 6.32%, which was comparable to a Pt CE-based DSSC (6.38%) under one sun illumination. Similarly, the maximum incident photon-to-charge carrier efficiency exhibited by MoS
2 CE-based DSSCs was 65.84%, which was also comparable to a Pt CE-based DSSC (68.38%). The study demonstrated that the marigold flower-like nanostructured MoS
2 films are a promising alternative to the conventional Pt-based CEs in DSSCs.
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