Ionic liquid integrated polyethylene glycol (PEG)-based quasi-solid electrolyte for efficiency enhancement of dye-sensitized solar cell

Abstract

We are presenting herein the effect of using three different cell electrolytes namely: (a) propylene carbonate containing 0.2 M LiI and 0.02 M I 2; (b) a polymer electrolyte, same as (a) having polyethylene glycol (PEG) as polymer matrix; and (c) polymer electrolyte same as (b) with added ionic liquids, 1, 2-dimethyl-3-propylimidazolium iodide or 1-ethyl-3-methylimidazolium iodide on the performance of TiO2-based dye-sensitized solar cells (DSSCs). Electrolytes were structurally characterized using FTIR spectra, and their thermal stability was studied through TGA in the temperature range of 30–600 °C. Fabricated cells with varied composition of the cell electrolyte were assessed for their electrical outputs (J SC, V OC, η etc.) and EIS characteristics. Ionic liquid imbibed polymer electrolyte demonstrated improved thermal stability and higher room temperature ionic conductivity of 4.48 mS cm−1. DSSC composed of the polymer electrolyte with 1-ethyl-3-methylimidazolium iodide has shown an open-circuit voltage V oc = 0.75 V, a short-circuit current density J sc = 3.61 mA/cm2, fill factor FF = 0.51, and overall conversion efficiency η = 1.6% under irradiance of 100 mW cm−2. The conversion efficiency was enhanced by 60% with added ionic liquid compared to DSSC employing PEG-based polymer electrolyte. An increase in charge-transfer resistance (R ct) with increasing PEG concentration in the cell electrolyte from 20 to 60% and decrease with the addition of ionic liquids were observed. The cell performance at elevated temperatures was assessed by determining the photocurrent–potential curves for the cells with different electrolytes at temperatures ranging from 30 to 60 °C. The temperature variation resulted in strong influence on J SC, but the effect over V OC was insignificant.