In situ sulfidation of porous sponge-like CuO/SiWCo into CuS/SiWCo as stabilized and efficient counter electrode for quantum dot-sensitized solar cells.

Quantum dot-sensitized solar cells (QDSSCs), which are cost-effective, facilely prepared and environmentally friendly, are regarded as a promising third-generation photovoltaic technology, although the conversion efficiency of QDSSCs is still far lower than the theoretical efficiency (44%). Furthermore, the traditional CuS/brass counter electrode (CE) is susceptible to continuous corrosion from the polysulfide electrolyte, reducing the stability and electrocatalytic activity of the CE, thereby affecting cell performance. To enhance the stability of the CuS CE and make full use of its excellent catalytic properties, we used eco-friendly polyoxometalates (KSiWOCo(ii) (HO), SiWCo) and porous sponge-like CuO as precursors to prepare a novel SiWCo-doped high-efficiency CuS/SiWCo CE on FTO by adopting the method of in situ sulfidation in the electrolyte. Electrochemical analysis revealed that the novel CuS/2%-SiWCo (CuS-2) CE exhibits extremely high stability and electrocatalytic performance compared with other electrodes. Meanwhile, adding an appropriate amount of SiWCo can inhibit charge recombination and improve cell performance. The CdS/CdSe co-sensitized QDSSCs assembled with the novel CuS-2 CE obtained a power conversion efficiency (PCE) of 5.94%, which was 20% more efficient than QDSSCs based on CuS/brass CE (4.96%). The method reported here puts forth a new direction for the preparation of efficient CuS counter electrodes.