Pulse potentiostatic electropolymerization of high performance PEDOT counter electrodes for Pt-free dye-sensitized solar cells

Abstract

High performance nano-meadows poly(3,4-ethylenedioxythiophene) (PEDOT) were electropolymerized onto the fluorinated tin oxide (FTO) substrates as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) by using the pulse potentiostatic electropolymerization method. Various pulse parameters were studied to control the morphology of PEDOT films. After optimization, a PEDOT film with nano-meadows morphology can be obtained under 1.2V pulse-on potential, 0.2V pulse-reversal potential, 1s pulse-on period, 0.5s pulse-reversal period, and total 900 duration time. The extensive cyclic voltammograms (CV) showed the nano-meadows PEDOT CE with excellent electrocatalytic activity for I3− reduction. Moreover, the peak current densities of the nano-meadows PEDOT CE showed no sign of degradation after consecutive 300 CV tests, suggesting the great electrochemical stability of the PEDOT CE. The electrochemical impedance spectroscopy showed the pulsed PEDOT CE has the lowest charge-transfer resistance (RCT) of 1.27Ωcm2 among all CEs tested in this study. Thus, the DSSC assembled with the pulsed PEDOT CE showed an enhanced photovoltaic conversion efficiency of 6.40% (compared to 5.75% for DSSCs with Pt CE) under full sunlight illumination (100mWcm−2, AM1.5 G) due to its intrinsic superior electrocatalytic activity and high surface area from the nano-meadows morphology. Therefore, the pulsed PEDOT CE can be considered as a promising alternative CE for use in low-cost Pt-free DSSCs.