Dye-Sensitized Solar Cells Based on Deep Eutectic Solvent Electrolytes: Insights from Experiment and Simulation

Abstract

In the present study, we examined a choline chloride–ethylene glycol (ChCl–EG) deep eutectic solvent (DES) mixed with different iodide salts as electrolytes in dye-sensitized solar cells (DSSCs) by experiment and atomistic molecular dynamics simulations. The photovoltaic performance of DES-based DSSCs revealed that solar cells with an inorganic iodide source show higher performance than cells with an organic iodide source. In this case, the influence of potassium (K+) and 1-etyl-3-methylimidazolium (Emim+) counterions on the DSSC performance in DES-based electrolytes was studied. The photovoltaic and electrochemical properties revealed that the presence of KI salt in the electrolyte solution considerably enhances the DSSC efficiency. In this way, the effect of iodide sources on the viscosity, conductivity, and impedance spectra of DES electrolytes was investigated. Additionally, MD simulations of the TiO2/DES electrolyte and Pt/DES electrolyte interfaces suggest that K+ cations cover the surface of anatase TiO2. Furthermore, the dynamics of iodide anions in the KI system was found to be higher than that of K+ cations. The diffusion coefficient of K+ in the DES was found to be systematically lower compared to that of Emim+ due to the higher coordination of K+ ions with chloride ions and EG molecules.