Fabricating CuS counter electrode for quantum dots-sensitized solar cells via electro-deposition and sulfurization of Cu₂O

Highlights: • CuS/FTO CE is fabricated indirectly by electro-deposition of Cu₂O followed by sulfurization. • FTO substrates avoid continuous corrosion of substrates in the electrolyte. • The QDSC with CuS/FTO CE achieves a high fill factor of 0.50. • CuS/FTO has uniform and integral morphology of 3D flower-like nanosheets. - Abstract: CuS/FTO counter electrode (CE) with flower-like nonosheets structure was fabricated through electro-deposition of Cu₂O followed by sulfurization. This electrochemical method has better control over the morphology of CuS/FTO CE. And the application of FTO can avoid the continuous corrosion of Cu substrate in polysulfide electrolyte. Besides, through the optimization of electro-deposition, the CuS/FTO CE obtains excellent photoelectrochemical performance (photoelectric conversion efficiency (PCE) = 4.07%, fill factor (ff) = 0.50) which is much higher than Pt CE (PCE = 1.90%) and Cu₂S/Cu CE (PCE = 3.76%) prepared by directly immersing copper into polysulfide electrolyte. Therefore, the CuS/FTO CE prepared by electro-deposition of Cu₂O followed by sulfurization has shown much promise.