An in situ inward etching strategy for constructing a p-p heterojunction Cu2S/Cu2-xSe material based on brass as an effective counter electrode for quantum dot sensitized solar cells

Composite counter electrode Cu2S/Cu2-xSe nanosheets based on brass are fabricated by an in situ inward etching method using Cu(OH)(2) nanotubes as a template. Due to superior electrocatalytic activity towards the polysulfide electrolyte, the quantum dot-sensitized solar cells constructed with Cu2S/Cu2-xSe counter electrodes deliver a considerable power conversion efficiency of 6.10% under 1 sun illumination, which is a 22% enhancement compared to that of Cu2S/brass (5.00%). According to the results of BET testing, solid-state J-V measurements and transient photocurrent measurements, the enhanced electrocatalytic activity is attributed to two aspects: one is the larger surface active area, which provides more active sites for the electrolyte, and the other is the formation of a p-p heterojunction for more effective electron transfer in the counter electrode. In addition, the band energy structure of the Cu2S/Cu2-xSe heterojunction is further investigated to understand the behavior of interfacial electron transfer. Finally, the outstanding electrochemical catalytic activity and stability of the Cu2S/Cu2-xSe counter electrode are proved by electrochemical impedance spectroscopy, Tafel polarization and cyclic voltammetry results for symmetric dummy cells, demonstrating that the Cu2S/Cu2-xSe composite is a desirable material as a counter electrode for quantum dot-sensitized solar cells.