The Role of Confined Water in Ionic Liquid Electrolytes for Dye-Sensitized Solar Cells.
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-principles-based 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).
†Graduate School of Energy Environment Water Sustainability (EEWS), Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Republic of Korea.
Jiwon
J
Jeon
†Graduate School of Energy Environment Water Sustainability (EEWS), Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Republic of Korea.
Hyungjun
H
Kim
†Graduate School of Energy Environment Water Sustainability (EEWS), Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Republic of Korea.|‡Materials and Process Simulation Center, Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States.|∥World Class University (WCU) Project, EEWS, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea.
William A
WA
Goddard
†Graduate School of Energy Environment Water Sustainability (EEWS), Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Republic of Korea.|‡Materials and Process Simulation Center, Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States.
Tod A
TA
Pascal
§Materials Science, Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Republic of Korea.
Ga-In
GI
Lee
†Graduate School of Energy Environment Water Sustainability (EEWS), Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Republic of Korea.|§Materials Science, Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Republic of Korea.
Jeung Ku
JK
Kang
dye-sensitized solar cells; electrolytes; ionic liquids