Pt-free counter electrode based on orange fiber-derived carbon embedded cobalt sulfide nanoflakes for dye-sensitized solar cells

Abstract There is an increasing attention to develop Pt-free counter electrodes to further reduce the production cost of dye-sensitized solar cells (DSSCs). In this paper, we proposed a nanocomposite of a naturally derived carbon dot and cobalt sulfide which was prepared by a one-pot solvothermal method. The oxidation of the orange fiber and the formation of cobalt sulfide structures were confirmed by various characterization tools, such as thermogravimetric, energy-dispersive X-ray, X-ray powder diffraction and X-ray photoelectron spectroscopic analyses. The scanning electron microscopy and N2 porosimeter studies revealed nanoflake-like structures with an abundance of mesopores with a pore diameter of 4-15 nm. The electrocatalytic activity of the product obtained from electrochemical impedance spectroscopy was found to be close to that of Pt due to the increase of electrocatalytic active sites. Under the illumination of AM 1.5 simulated solar light, the DSSC based on the cobalt sulfide/carbon composite counter electrode achieves a power conversion efficiency of 5.94 % which is higher than the Pt-based electrode (5.57 %).