Rational design and fabrication of skeletal Cu7S4 nanocages for efficient counter electrode in quantum dot-sensitized solar cells

Abstract The widely used brass based Cu 2 S counter electrodes (CEs) cannot stand the continuing corrosion in polysulfide electrolyte, which has limited the development of quantum dot-sensitized solar cells. Here, skeletal Cu 7 S 4 nanocages (SKE-Cu 7 S 4 ) with symmetric opening windows were rational designed and synthesized by kinetic roughening processes, and a possible formation mechanism had been proposed. Furthermore, SKE-Cu 7 S 4 onto fluorine-doped tin oxide glass substrates were designed and deposited to function as new efficient, stable and low cost CEs. Thanks to the 3D opening structure of SKE-Cu 7 S 4 CEs, the assembled QDSSCs exhibited a power conversion efficiency of 4.43% under 1 sun (100 mW cm −2 ) irradiation, while those of preformed 18 facet-Cu 7 S 4 , Pt and brass/Cu 2 S CEs are of 3.87%, 1.73% and 3.32%, respectively. Further studies by cyclic voltammetry measurements indicate the SKE-Cu 7 S 4 CEs still remain good cyclability after 600 cycles, demonstrating a super stable capability, while the commonly used brass/Cu 2 S CEs show obvious fluctuation.