Synthesis of double-shelled copper chalcogenide hollow nanocages as efficient counter electrodes for quantum dot-sensitized solar cells

Double-shelled copper chalcogenide (Cu_2−xSe and Cu₇S₄) nanocages of about 250 nm sizes are synthesized respectively by using Cu₂O nanocubes as sacrificial precursor via Kirkendall diffusion and etching. Both the double-shelled Cu_2−xSe and Cu₇S₄ nanocages are demonstrated to be excellent counter electrode (CE) materials in quantum dot-sensitized solar cells (QDSSCs) and exhibit high electrocatalytic activities for polysulfide electrolyte regeneration. The QDSSCs using the double-shelled Cu_2−xSe and Cu₇S₄ nanocages as CEs show power conversion efficiencies (PECs) of 4.76 and 4.53%, respectively, which are 19.6% and 15.3% higher than the corresponding devices using the single-shelled Cu_2−xSe and Cu₇S₄ nanocages as CEs. The overall enhancement of photovoltaic performance including the fill factor, short-circuit current density and PEC is attributed to the larger CE-electrolyte interface provided by the double-shelled nanocages facilitating fast electron transfer in the QDSSCs.