Lithium-functionalized graphene oxide with a low load of Pt as an efficient counter electrode for dye-sensitized solar cells

Low-cost materials with excellent chemical stability, high conductivity, and catalytic properties have attracted much attention as an alternative to conventional Pt counter electrodes in dye-sensitized solar cells (DSSCs). Herein, graphene oxide (GO) sheets were successfully synthesized via the improved Hummers’ method, functionalized with lithium and characterized by SEM, AFM, XRD, Raman, UV-Vis, and FTIR techniques. The impact of GO thickness, heat treatment temperature, and hybridization with Pt particles on photovoltaic performance of the counter electrodes (CEs) were studied. A solar efficiency of 2.47% and 2.94% was achieved for the pristine GO and Li-functionalized GO electrodes, respectively under an optimized condition. A hybrid structure of GO or Li-functionalized GO films coated with an ultra-thin Pt film (i.e., GO-Pt or LiGO-Pt CEs) led to a remarkable efficiency of 7.07% and 8.87%, respectively. Such superior photovoltaic performance of LiGO-Pt CE indicated an increase of 61% in cell efficiency compared to the conventional Pt counter electrodes. The design of GO-based counter electrodes decorated with Pt deposition and Li functionalization will open a new concept for improvement of power conversion efficiency of DSSCs.