Understanding the Role of Reduced Graphene Oxide in the Electrolyte of Dye-Sensitized Solar Cells

One of the major drawbacks in dye-sensitized solar cells (DSSC) is related to the use of a liquid electrolyte, which limits durability and stability. Part of this problem can be solved by replacing the liquid electrolyte by a polymer or gel electrolyte, although the open circuit potential (V-OC) of the solar cells is affected. In this work, the role of the reduced graphene oxide (RGO) added to a gel electrolyte in order to improve the efficiency of DSSCs is discussed in detail. The gel polymer electrolyte is composed of poly(ethylene oxide) (PEO), gamma-butyrolactone (GBL), LiI, I-2, and different concentrations of RGO. The best solar cell using 0.5 wt % of RGO delivered an efficiency of 5.07 +/- 0.97%, with the highest values of I-sc and V-OC. RGO sheets are acting as a multipurpose component in the electrolyte. The recovery of the V-OC values can be related to the removal of polyiodide species from the photoanode surface by interaction with the RGO sheets. The increase in the I-sc, is assigned to the enhancement in the diffusion of I-3(-) species and by the reduction of the electron transfer resistance in the counter electrode.