Urea-treated electrolytes for higher efficiency dye-sensitized solar cells

Urea was used as additive for the triiodide/iodide electrolyte (I-/I3-) to increase the efficiencies of dye-sensitized solar cells (DSSCs). Different concentrations (0, 2, 5, 10, and 20 wt %.) of urea were added to the electrolyte to improve overall DSSC performance. The optimal concentration was found at 10 wt %. Significant improvements were achieved in both open circuit voltage (V_oc) and fill factor (FF) by increasing the urea wt %. Urea is considered a Brønsted-Lowry base that has a lone pair of electrons. The power conversion efficiency (PCE %) was remarkably improved from -8.5% without the use of urea to ∼10.1% for the optimal 10 wt % of urea in the electrolyte. The efficiency enhancement was attributed mainly to the decrease of triiodide (I₃^-) in the electrolyte due to the higher urea wt % and the enhanced intermolecular hydrogen bonding between the urea and electrolyte when the excess H⁺ was introduced to the electrolyte at a higher urea wt %.