Highly Electrocatalytic Cu2ZnSn(S1−xSex)4 Counter Electrodes for Quantum-Dot-Sensitized Solar Cells

ACS Applied Materials & Interfaces 5(3) 479-484 https://doi.org/10.1021/am302522c

Yuebin Cao, Yanjun Xiao, Jin-Young Jung, Han-Don Um, Sang-Won Jee, Hye Mi Choi, Jin Ho Bang and Jung-Ho Lee

Abstract

Traditional Pt counter electrode in quantum-dotsensitized solar cells suffers from a low electrocatalytic activity and instability due to irreversible surface adsorption of sulfur species incurred while regenerating polysulfide (Sn 2−/S2−) electrolytes. To overcome such constraints, chemically synthesized Cu2ZnSn(S1−xSex)4 nanocrystals were evaluated as an alternative to Pt. The resulting chalcogenides exhibited remarkable electrocatalytic activities for reduction of polysulfide (Sn 2‑) to sulfide (S2−), which were dictated by the ratios of S/Se. In this study, a quantum dot sensitized solar cell constructed with Cu2ZnSn(S0.5Se0.5)4 as a counter electrode showed the highest energy conversion efficiency of 3.01%, which was even higher than that using Pt (1.24%). The compositional variations in between Cu2ZnSnS4 (x = 0) and Cu2ZnSnSe4 (x = 1) revealed that the solar cell performances were closely related to a difference in electrocatalytic activities for polysulfide reduction governed bythe S/Se ratios.