Facile synthesis of cobalt sulfide/carbon nanotube composites as a low-cost Pt-free counter electrode for dye-sensitized solar cells (DSSCs)

Abstract

In this work, a nanocomposite of CoS2 with multiwalled carbon nanotubes (MWCNTs) has been prepared using simple hydrothermal technique. Further, CoS2/CNT composite was charecterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption-desorption to study the crystallinity, surface morphology chemical composition with chemical states and textural properties, respectively. The cyclic voltammetric tests recorded an enhanced electrocatalytic activity when the CoS2 was deposited onto the surface of the MWCNTs. Additionally, consecutive cyclic voltammetric tests demonstrated that the CE possessed excellent electrochemical stability. Thus, the DSSC assembled with CoS2/MWCNT CE showed an enhanced photovoltaic conversion efficiency of 8.85 ± 0.03 % (compared to 1.84 ± 0.03 % for DSSCs with MWCNT CE or 2.87 ± 0.04 % for CoS2 CE alone) under full sunlight illumination (100 mW cm−2, AM1.5 G) due to the superior electrocatalytic activity of the out-shell CoS2 material and highly specific surface of the MWCNTs. Therefore, the CoS2/MWCNT composite can be considered as a promising alternative CE for use in low-cost DSSCs.