The Role of Confined Water in Ionic Liquid Electrolytes for Dye-Sensitized Solar Cells

Abstract

Ionic liquids (ILs) provide an attractive medium for various chemical and redox reactions, where they are generally regarded as hydrophobic. However, Seddon et al. discovered that 4−10 wt % water absorbs into ILs that contain bulky anions, and Cammarata et al. found that the molecular state of water in ILs is dramatically different from that of bulk liquid water or that of water vapor. To determine the microstructure of water incorporated into ILs and the impact on properties, we carried out first-principlesbased molecular dynamics simulations. We find water in three distinct phases depending on water content, and that the transport properties depend on the nature of the water phases. These results suggest that the optimal water content is ∼10% mole fraction of water molecules (∼1.1 wt %) for applications such as nonvolatile electrolytes for dye-sensitized solar cells (DSSCs). This suggests a strategy for improving the performance of IL DSSC by replacing water with additives that would play the same role as water (since too much water can deteriorate performance at the anode−dye interface).

Broadband energy transfer to sensitizing dyes by mobile quantum dot mediators in solar cells

“…These ligands were exchanged with a thiol ligand (2–(dimethyl amino) ethane–thiol) and were dispersed in a conductive ionic liquid (1–ethyl–3–methylimidazolium bis (trifluromethylsulfonyl) imide) using the extraction process within solution phases as illustrated in the Supplementary Information (Figure S1a). The electrolyte was mixed with a proper combination of cation (EMIm–I or DMPII), anion (I 2 ), charge transport enhancer (LiI), recombination inhibitor (tBP), and water8. Then, the solution was directly injected into the DSSCs (Figure S1b).…”

The Electric Double Layer in an Ionic Liquid Incorporated with Water Molecules: Atomic Force Microscopy Force Curve Study

“…The presence of water also remarkably affects the surface structure of ILs, such as the number and orientation of ions at the surface, which further change the surface tension of the ILs . However, it was reported that the presence of water in ILs can promote the diffusion of redox species and increase the corrosion rate of alloys . Most importantly, a small amount of water could possibly change the structure of the electric double layer (EDL) and thus the kinetic parameters of electroactive species at the electrochemical interface .…”

Stable dye-sensitized solar cells based on a gel electrolyte with ethyl cellulose as the gelator

“…I -may also assist the current flow. In such cases, rapid charge transfer is enabled even in a viscous medium, as physical transfer of species is not necessary for charge transport [42][43][44].…”