A novel binary electrolyte 1-allyl-3-methylimidazolium dicyanamide ionic liquid/acetonitrile-iodide for sustainable dye-sensitized solar cells

Abstract

A novel binary electrolyte composed of the planar structured 1-allyl-3-methylimidazolium dicyanamide (AMIM-DCA) ionic liquid (IL) mixed with acetonitrile-based iodide/tri-iodide electrolyte was prepared for sustainable dye-sensitized solar cells (DSSCs). Under a 2.56 mW.cm⁻² light-emitting diode (LED), binary electrolyte cells (20 wt% AMIM-DCA) showed a significant increase in open-circuit voltage (V_oc) (628 mV, i.e., + 26.7% compared to cells without IL) and electron lifetime (43 ms, compared to 19 ms for cells without IL), which means a reduction in the dark current. Meanwhile, the short-circuit photocurrent density (J_sc) decreased due to the increase in viscosity, a result consistent with the increase in charge transfer resistance (R_ct) at the photoanode/electrolyte interface. The conversion efficiency (η) of cells with 20 wt% IL (η = 2.59%) increased by 20% compared to cells without IL (η = 2.16%). The AMIM-DCA ionic liquid, being placed by its positive cation (AMIM⁺) near the photoanode, competes with the oxidant I₃⁻ and reduces the dark current. The fill factor (ff) also reached 58.5% with 20 wt% IL, compared to 49.4% without IL. The IL improved the stability of the cells under solar irradiation: the reduced volatility of the electrolyte compensates for the quality of the sealing. Operating temperatures increase the fluidity of the binary electrolyte over time, thereby increasing the J_sc and η (+ 45.4% after 30 min of solar irradiation). This indicates better thermal stability and extended cell lifecycle.