The use of 1-ethyl-3-methylimidazolium iodide ionic liquid in dye sensitized solar cells: A joint experimental and computational perspective

Abstract

The photovoltaic performance of dye-sensitized solar cells (DSSCs) significantly depends on the components of electrolyte solution. In this study, the electrolytes involving acetonitrile (ACN) solvent and various salts namely potassium iodide (KI), 1-ethyl-3-methylimidazolium iodide ionic liquid ([C2mim]I ∼ Emim-I IL), sodium thiocyanate (NaSCN), and ammonium thiocyanate (NH4SCN) were fabricated and their effects on the DSSC performance were explored. Among the different inorganic (KI) and organic (Emim-I) iodide sources, the DSSC showed high performance when KI and Emim-I mixed. In the meantime, without KI, by increasing Emim-I concentration from 0.3 M to 1.2 M, the best efficiency of DSSC was obtained for 0.9 M concentration. The results indicated that the best performance of the cells can be obtained when Emim-I and NH4SCN were added to the 0.6 M of KI solution. Power conversion efficiency as high as 11.07 % was obtained under the best operation conditions. Beside experiments, the interface of solid/liquid electrolyte was also studied as a key element of DSSCs by using molecular dynamics simulations. The influence of cations such as K+, and 1-ethyl-3-methylimidazolium (Emim+), Na+, and NH4+ on the double-layer structure in ACN-based electrolytes at the anatase TiO2(101) and platinum surfaces was studied. Particularly, a strong impact of cations on the I− and SCN− anions density distribution at the interface was found.