Effect of electropolymerization time on the performance of poly(3,4-ethylenedioxythiophene) counter electrode for dye-sensitized solar cells

Poly (3,4-ethylenedioxythiophene) (PEDOT) films were synthesized onto the fluorinated tin oxide (FTO) substrates as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) through an aqueous galvanostatic polymerization technique. Polymerization time was employed to control the surface morphologies and performances of the PEDOT films. The PEDOT electrodes showed faster reaction rate and higher electrocatalytic activity for I ₃ ^- reduction as the polymerization time increased, which contributed to the increase of the open circuit voltage (V _OC ) for the DSSCs. The electrochemical impedance spectroscopy (EIS) indicated that charge transfer resistance (R _ct ) at CE/electrolyte interface decreased and then rebounded with the increasing polymerization time. Thus the short circuit photocurrent density (J _SC ) and fill factor (FF) of the DSSCs changed with the same trend. The energy conversion efficiency of the DSSC based on PEDOT CE up to 6.46% was achieved, which was higher than that based on Pt CE (6.33%). Therefore, the PEDOT film can be considered as a promising alternative CE for Pt-free DSSCs.