Highly Efficient Dye-Sensitized Solar Cells Based on Electrolyte Solutions Containing Choline Chloride/Ethylene Glycol Deep Eutectic Solvent: Electrolyte Optimization

Abstract

Combined experimental and computational analyses were carried out with the aim of developing a cost-effective and sustainable electrolyte solution based on a deep eutectic solvent (DES) for dyesensitized solar cells (DSSCs). A mixture of choline chloride (CholCl, 1 mol) and ethylene glycol (EG, 2 mol) as a DES was used in combination with MeCN, lithium iodide, 1-ethyl-3-methylimidazolium iodide (Emim), and iodine as DSSC electrolytes on TiO 2 and Pt electrodes. It is noteworthy that in this work the effects of various conditions, namely, the amount of MeCN and the molar concentration of I 2 , LiI, and EmimI and the 4-tert-butylpyridine (TBP) additive on the photovoltaic performance of DSSCs were evaluated. Optimization of the DSSC performance using photocurrent density−voltage plots allowed reaching an efficiency of 9.26% with an electrolyte solution comprising LiI (1.1 M), EmimI (0.5 M), and I 2 (0.04 M), and 60:40 v/v of CholCl/EG DES and MeCN. Addition of TBP to the electrolyte allowed reaching even 9.48%, both are unprecedentedly high values. Density functional theory geometry optimizations and molecular dynamics simulation calculations generated an insightful set of information about the intensity of the interactions between electrolyte components with each other in solution and with the TiO 2 or Pt solid surfaces. From mean square displacement curves, diffusion coefficients (×10 −11 m 2 /s) were found to increase along the series Li + (0.82) < Emim + (1.01) < Chol + (1.15) < Cl − (1.29) < I − (1.74) < EG (5.99) < MeCN (102.92) in line with the experimental data. Li + solvation vs Li + adsorption on the TiO 2 or Pt surface is the main interaction governing the efficiency with a high rate of localization, improving the performance. Our results provide a deep understanding of the molecular interactions at the interfaces of the DES and might pave the way for the fabrication and design of optimized DES-based electrolytes for photovoltaic processes.

A Review of Third Generation Solar Cells

“…In a DSSC, the electrolyte is another very important component as it can affect the stability and performance of a cell [75]. The redox couple, organic solvent, and additives are the essential components of an electrolyte.…”

Protection coatings for corrosion control of mild steel using phenolic polymeric deep eutectic solvents

“…24 In another example, M. Isik et al showed the versatility of polyDES chemistry and their applications as sorbents for CO 2 capture. 25 Beyond this, polyDESs have also been investigated as electrolytes, 26,27 as carriers for drug delivery systems, 28 and in coating applications. 29 Our group recently reported the development of DESs based on polyphenols, which showed potential as (bio)adhesives.…”