Sulfur-doped reduced graphene oxide/MoS2 composite with exposed active sites as efficient Pt-free counter electrode for dye-sensitized solar cell

Abstract

Low-cost catalysts possessing merits of high conductivity and plenty of active sites are highly desirable for the developing of Pt-free counter electrode (CE) in dye-sensitized solar cells (DSCs). In this study, porous sulfur-doped reduced graphene oxide/MoS2 (S-rGO/MoS2) composites were successfully synthesized via a simple one-step annealing strategy employing CS2 as sulfur source. Electrochemical measurements revealed that the as-prepared composite presented a superior catalytic activity on the triiodide reduction process, comparable with Pt electrode. Under optimized conditions, a power conversion efficiency of 6.96% was achieved for the N719-sensitized solar cell with a S-rGO/MoS2 CE, which is very close to that for the device containing a thermally deposited Pt CE (7.35%). The outstanding electro-catalytic activity of composite was attributed to the exposed numerous edges providing much more active sites, and good conductivity resulting from two-dimensional conductive networks of both S-rGO and MoS2. This work demonstrated S-rGO/MoS2 composite as a promising alternative for noble metal Pt in triiodide reduction process and a simple approach of employing two-dimensional nanomaterials as multifunctional materials in photovoltaic for mass application.